"have failed" is the correct option because it is in the present perfect tense, which is used to indicate that an action has been completed in the past but has a connection to the present. "Fail" is in the present simple, which is not appropriate in this context because the action is completed. "Had failed" is in the past perfect, which is used to indicate that an action was completed before another action in the past. This option doesn't match the context of the sentence, as there's no other action in the past that this is being compared to. "Was failing" is in the past continuous, which is used to indicate that an action was in progress at a specific time in the past. But this option doesn't match the context of the sentence, as the speaker is describing the result, not the progress of the action.
Simple Present
The simple present or present simple is a form that combines present tense with "simple" (neither perfect nor progressive) aspect.
In the indicative mood it consists of the base form of the verb, or the -s form when the subject is third-person singular (the verb be uses the forms am, is, are). However, with non-auxiliary verbs it also has a periphrastic form consisting of do (or third-person singular does) with the bare infinitive of the main verb — this form is used in questions (and other clauses requiring inversion and negations, and sometimes for emphasis.
The principal uses of the simple present are given below.
To refer to an action or event that takes place habitually. Such uses are often accompanied by frequency adverbs and adverbial phrases such as always, often, from time to time and never.
Examples:
- I always take a shower.
- He writes for a living.
This contrasts with the present progressive, which is used for actions taking place at the present moment.
With stative verbs in senses that do not use progressive aspect, to refer to a present or general state, whether temporary, permanent or habitual. (In senses that do use progressive aspect, the present simple is used when the state is permanent or habitual.)
- You are happy.
- I know what to do.
- Denmark lies to the north of Germany.
When quoting someone or something, even if the words were spoken in the (usually very recent) past:
- The label says "External use only".
- Mary says she's ready.
To refer to a single completed action, as in recounting the events of a story in the present tense (see historical present), and in such contexts as newspaper headlines, where it replaces the present perfect:
- In Hamlet, Ophelia drowns in a stream.
- 40-year-old wins gold medal.
Sometimes to refer to an arranged future event, usually with a reference to time:
- We leave for Berlin tomorrow at 1 pm.
In providing a commentary on events as they occur, or in describing some theoretical sequence of events:
- I chop the chives and add them to the mixture.
- According to the manager's new idea, I welcome the guests and you give the presentation.
In many dependent clauses referring to the future, particularly condition clauses, clauses expressing place and time, and many relative clauses (see below):
- If he finds your sweets, he will eat them.
- We will report as soon as we receive any information.
In certain situations in a temporal adverbial clause, rather than the present progressive:
- We can see the light improving as we speak.
In colloquial English it is common to use can see, can hear for the present tense of see, hear, etc., and have got for the present tense of have (denoting possession.
See have got and can see below.
For the present subjunctive, see subjunctive.
For uses of modal verbs (which may be regarded as instances of the simple present) see modal verbs.
Present progressive
The present progressive or present continuous form combines present tense with progressive aspect. It thus refers to an action or event conceived of as having limited duration, taking place at the present time. It consists of a form of the simple present of be together with the present participle of the main verb and the ending -ing.
- We are cooking dinner now.
This often contrasts with the simple present, which expresses repeated or habitual action (We cook dinner every day). However, sometimes the present continuous is used with always, generally to express annoyance about a habitual action:
- You are always making a mess in the study.
Certain stative verbs do not use the progressive aspect, so the present simple is used instead in those cases. The present progressive can be used to refer to a planned future event:
- We are tidying the attic tomorrow.
It also appears with future reference in many condition and time clauses and other dependent clauses:
- If he*'s sleeping* when you arrive, wake him up.
- I will finish the job while the children are playing.
It can also refer to something taking place not necessarily at the time of speaking, but at the time currently under consideration, in the case of a story or narrative being told in the present tense (as mentioned above under present simple):
- The king and queen are conversing when Hamlet enters. For the possibility of a present subjunctive progressive, see English subjunctive.
Present Perfect
The present perfect (traditionally called simply the perfect) combines present tense with perfect aspect, denoting the present state of an action's being completed, that is, that the action took place before the present time. (It is thus often close in meaning to the simple past tense, although the two are not usually interchangeable.) It is formed with the present tense of the auxiliary have (namely have or has) and the past participle of the main verb.
The choice of present perfect or past tense depends on the frame of reference (period or point in time) in which the event is conceived as occurring. If the frame of reference extends to the present time, the present perfect is used. For example:
- I have written a letter this morning. (if it is still the morning)
- He has produced ten plays. (if he is still alive and professionally active)
- They have never traveled abroad. (if they are still alive and considered capable of traveling)
If the frame of reference is a time in the past, or a period that ended in the past, the past tense is used instead. For example:
- I wrote a letter this morning (it is now afternoon);
- He produced ten plays (he is now dead or his career is considered over, or a particular past time period is being referred to);
- They never traveled abroad (similarly).
See Simple past for more examples.
The simple past is generally used when the occurrence has a specific past time frame – either explicitly stated (*I wrote a book in 1995; *the water boiled a minute ago), or implied by the context (for example, in the narration of a sequence of events). It is therefore normally incorrect to write a sentence like I have written a novel yesterday; the present perfect cannot be used with an expression of past time such as yesterday.
With already or yet, traditional usage calls for the present perfect: ''Have you eaten yet? Yes, I've already eaten.* However, current informal American speech tends to use the simple past: *Did you eat yet? Yes, I ate already.''
Use of the present perfect often draws attention to the present consequences of the past action or event, as opposed to its actual occurrence. The sentence she has come probably means she is here now, while the simple past she came does not. The sentence, "Have you been to the fair?" suggests that the fair is still going on, while the sentence, "Did you go to the fair?" could mean that the fair is over. (See also been and gone below.) Some more examples:
- I have eaten. (implies that I'm no longer hungry)
- We have made the dinner. (implies that the dinner is now ready to eat)
- The weather has gotten cloudier. (implies that it is now more cloudy than previously)
It may also refer to an ongoing state or habitual action, particularly in saying for how long, or since when, something is the case. For example:
- I have lived in Paris for five years.
- He has held the record since he won his Olympic gold.
- We have eaten breakfast together every morning since our honeymoon.
This implies that I still live in Paris, that he still holds the record and that we still eat together every morning (although the first sentence may also refer to some unspecified past period of five years).
When the circumstance is temporary, the present perfect progressive is often appropriate in such sentences (see below); however, if the verb is one that does not use the progressive aspect, the basic present perfect is used in that case too:
- Amy has been on the swing for ten minutes.
The present perfect may refer to a habitual circumstance, or a circumstance being part of a theoretical or story narrative being given in the present tense (provided the circumstance is of an event's having taken place previously):
- Whenever I get home, John has usually already arrived.
- According to the plan, the speeches have already been given when the cake is brought out.
The present perfect may also be used with future reference, instead of the future perfect, in those dependent clauses where future occurrence is denoted by present tense. For example:
- When you have written it, show it to me.
Present Perfect Progressive
The present perfect progressive (or present perfect continuous) construction combines some of this perfect progressive aspect with present tense.
It is formed with the present tense of have (have or has), the past participle of be (been), and the present participle of the main verb and the ending "-ing"
This construction is used for ongoing action in the past that continues right up to the present or has recently finished:
- I have been writing this paper all morning.
- Why are his eyes red? He has been crying.
It is frequently used when stating for how long, or since when, something is the case:
- She has been working here since 1997.
- How long have you been sitting there?
- They have been arguing about it for two weeks.
In these sentences the actions are still continuing, but it is the past portion of them that is being considered, and so the perfect aspect is used. (A sentence without perfect aspect, such as I am sitting here for three hours, implies an intention to perform the action for that length of time.)
With stative verbs that are not used in the progressive, and for situations that are considered permanent, the present perfect (nonprogressive) is used instead.
Perfect
The perfect aspect is used to denote the circumstance of an action's being complete at a certain time. It is expressed using a form of the auxiliary verb have (appropriately conjugated for tense etc.) together with the past participle of the main verb: She has eaten it; We had left; When will you have finished?
Perfect forms can also be used to refer to states or habitual actions, even if not complete, if the focus is on the time period before the point of reference (We had lived there for five years). If such a circumstance is temporary, the perfect is often combined with progressive aspect.
The implications of the present perfect (that something occurred prior to the present moment) are similar to those of the simple past, although the two forms are generally not used interchangeably – the simple past is used when the time frame of reference is in the past, while the present perfect is used when it extends to the present.
For all uses of specific perfect constructions, see the sections on the present perfect, past perfect, future perfect and conditional perfect.
By using nonfinite forms of the auxiliary have, perfect aspect can also be marked on infinitives (as in should have left and expect to have finished working), and on participles and gerunds (as in having seen the doctor).
Note that while all of the constructions referred to here are commonly referred to as perfect (based on their grammatical form), some of them, particularly nonpresent and nonfinite instances, might not be considered truly expressive of the perfect aspect. This applies particularly when the perfect infinitive is used together with modal verbs: for example, he could not have been a genius might be considered (based on its meaning) to be a past tense of he cannot/could not be a genius; such forms are considered true perfect forms by some linguists but not others.
Perfect Progressive
The perfect and progressive (continuous) aspects can be combined, usually in referring to the completed portion of a continuing action or temporary state: I have been working for eight hours. Here a form of the verb have (denoting the perfect) is used together with been (the past participle of be, denoting the progressive) and the present participle of the main verb.
In the case of the stative verbs, which do not use progressive aspect, the plain perfect form is normally used in place of the perfect progressive: I've been here for half an hour (not I've been being here...).
Clause
A clause is a grammatical unit built around a verb that typically contains a subject and a predicate. Understanding clauses is essential because they are the core building blocks of every sentence you read, write, or speak.
What makes a clause?
At minimum, a clause needs a verb (the predicate) and, in most cases, a subject — the person or thing the verb says something about. The predicate can also include objects, complements, and modifiers.
- She laughed. — subject (she) + verb (laughed)
- The manager approved the budget yesterday. — subject + verb + object + modifier
Sometimes the subject is left out. This happens regularly in imperative sentences and non-finite clauses:
- Sit down. — no visible subject, but "you" is understood
- Walking home, I noticed the shop was closed. — the -ing clause has no stated subject
Types of clauses
There are two main types:
-
Independent clause (also called a main clause) — can stand on its own as a complete sentence. It contains a finite verb.
- I missed the bus.
-
Dependent clause (also called a subordinate clause) — cannot stand alone and needs an independent clause to make sense.
- Because I overslept — incomplete on its own
Combine them and you get a complex sentence:
- I missed the bus because I overslept.
A simple sentence has one independent clause. More complex sentences combine independent and dependent clauses in various ways.
Quick check: If you can remove a group of words from a sentence and it still has a subject + finite verb and makes sense on its own, that group is likely an independent clause.
Why clauses matter
Recognizing clause boundaries helps you punctuate correctly, avoid run-on sentences, and build more varied, natural-sounding writing. Once you can spot where one clause ends and another begins, sentence structure becomes much easier to manage.
Ready to practice? Try Complex Sentence for the basics, then move on to Complex Sentence: Adverbials or Participle Clauses: Shortening Sentences with -ing and Having + Past Participle to deepen your skills.
Adverb
An adverb is a word that modifies a verb, adjective, determiner, clause, preposition, or sentence. Adverbs typically express manner, place, time, frequency, degree, level of certainty, etc., answering questions such as how?, in what way?, when?, where?, and to what extent?. This function is called the adverbial function, and may be realized by single words (adverbs) or by multi-word expressions (adverbial phrases and adverbial clauses).
Adverbs are traditionally regarded as one of the parts of speech. However, modern linguists note that the term "adverb" has come to be used as a kind of "catch-all" category, used to classify words with various different types of syntactic behavior, not necessarily having much in common except that they do not fit into any of the other available categories (noun, adjective, preposition, etc.)
C1 | Advanced
C1 is the fifth of six levels in the Common European Framework of Reference for Languages (CEFR), sitting between B2 (Upper-Intermediate) and C2 (Proficiency). It's classified as Advanced — the stage where you stop translating in your head and start thinking in English.
What a C1 user can do
At this level, you're expected to handle complex, demanding language across a wide range of situations:
- Reading — You can understand long, complex texts, including specialized articles and technical instructions outside your own field. You pick up on implicit meaning, not just what's stated directly.
- Speaking — You express yourself fluently and spontaneously with minimal searching for words. You use language flexibly for social, academic, and professional purposes.
- Writing — You produce clear, well-structured, detailed text on complex subjects, with controlled use of organizational patterns, connectors, and cohesive devices.
- Listening — You follow extended speech even when it isn't clearly structured or when relationships between ideas are only implied.
What C1 grammar looks like
C1-level grammar goes well beyond accuracy with tenses and articles. You're expected to use advanced structures naturally, including:
- Inversion for emphasis (Rarely have I seen such dedication.)
- Mixed and advanced conditionals (Had she known, she would never have agreed.)
- Subjunctive forms in formal contexts (It's essential that he be informed.)
- Cleft sentences for focus (What concerns me is the timeline.)
- Complex noun phrases and nominalization (The government's repeated failure to act…)
The difference between B2 and C1 isn't just knowing these structures exist — it's using them appropriately and with control across different registers.
Self-check: If you can read an opinion piece in The Guardian or The Economist and follow the argument without a dictionary, and if you can write a structured response disagreeing with it, you're likely operating at C1.
How C1 fits in the CEFR scale
The CEFR has six levels: A1 → A2 → B1 → B2 → C1 → C2. C1 is where most universities and professional bodies set their language requirements for non-native speakers.
Ready to test yourself? Try Pass the Test to Determine Your English CEFR Level or go straight to the C1/C2-level test. You can also practice key C1 structures like Inversion and Conditional Subjunctive.
C2 | Proficiency
C2, also called Proficiency, is the highest level on the CEFR scale. Reaching this level means you can understand and produce English with near-native command — not just accurately, but with nuance, precision, and ease across virtually any context.
What C2 looks like in practice
At this level, you are expected to:
- Understand with ease virtually everything you hear or read, including abstract, structurally complex, or highly colloquial material.
- Express yourself spontaneously and precisely, choosing words that capture finer shades of meaning — even in unfamiliar or high-pressure situations.
- Produce clear, well-structured text on complex subjects, with controlled use of organizational patterns, connectors, and cohesive devices.
- Recognize implicit meaning in demanding, longer texts — picking up on irony, understatement, and unstated assumptions.
- Communicate fluently without noticeable searching for expressions, adapting your register naturally to academic, professional, or informal settings.
How C2 differs from C1
While a C1-level user handles complex language competently, a C2 user does so effortlessly and with subtlety. The difference often shows up in:
- Idiomatic range — C2 users draw on a full repertoire of idiomatic expressions, colloquialisms, and cultural references.
- Precision under pressure — they can reformulate, hedge, or sharpen their point in real time without losing fluency.
- Writing sophistication — their texts read as polished and naturally organized, not just grammatically correct.
In short, C2 is less about learning new grammar rules and more about mastering the flexible, context-sensitive use of everything you already know.
Test your level
If you think you're approaching C2, try one of these challenges to check:
Difficulty: Hard
Hard difficulty. Difficulty levels represent author's opinion about how hard a question or challenge is.