The present perfect tense is formed using the auxiliary verb "have" or "has" followed by the past participle of the main verb. In this case, the subject is "they," which requires "have" as the auxiliary verb, and the past participle of "to visit" is "visited." So, the correct answer is "have visited."
Verb
Verbs constitute one of the main word classes in the English language. Like other types of words in the language, English verbs are not heavily inflected. Most combinations of tense, aspect, mood and voice are expressed periphrastically, using constructions with auxiliary verbs.
Generally, the only inflected forms of an English verb are a third person singular present tense form in -s, a past tense, a past participle (which may be the same as the past tense), and a form ending in -ing that serves as a present participle and gerund. Most verbs inflect in a simple regular fashion, although there are about 200 irregular verbs; the irregularity in nearly all cases concerns the past tense and past participle forms. The copula verb be has a larger number of different inflected forms, and is highly irregular.
A typical English verb may have five different inflected forms:
- The base form or plain form (go, write, climb), which has several uses—as an infinitive, imperative, present subjunctive, and present indicative except in the third-person singular
- The -s form (goes, writes, climbs), used as the present indicative in the third-person singular
- the past tense or preterite (went, wrote, climbed)
- The past participle (gone, written, climbed) – this is identical to the past tense in the case of regular verbs and some irregular ones (here the first two verbs are irregular and the third regular)
- The -ing form (going, writing, climbing), used as a present participle, gerund, and (de)verbal nounThe verb be has a larger number of different forms (am, is, are, was, were, etc.), while the modal verbs have a more limited number of forms.
Some forms of be and of certain other auxiliary verbs also have contracted forms ( 's, 're, 've, etc.).
In English, verbs frequently appear in combinations containing one or more auxiliary verbs and a nonfinite form (infinitive or participle) of a main (lexical) verb.
Examples
The first verb in such a combination is the finite verb, the remainder are nonfinite (although constructions in which even the leading verb is nonfinite are also possible – see below). Such combinations are sometimes called compound verbs; more technically they may be called verb catenae, since they are not generally strict grammatical constituents of the clause.
- The dog was barking very loudly.
- My hat has been cleaned.
- Jane does not really like us.
As the last example shows, the words making up these combinations do not always remain consecutive.
Tenses, Aspects and Moods
The means English uses for expressing the three categories of tense (time reference), aspect and mood are somewhat conflated. English has only limited means for expressing these categories through verb conjugation, and tends mostly to express them periphrastically, using the verb combinations mentioned in the previous section. The tenses, aspects and moods that may be identified in English are described below (although the terminology used differs significantly between authors). Note that in common usage, particular tense–aspect–mood combinations such as "present progressive" and "conditional perfect" are often referred to simply as "tenses".
Simple Past
The simple past, past simple or past indefinite, sometimes called the preterite, is the basic form of the past tense in Modern English. It is used principally to describe events in the past, although it also has some other uses. Regular English verbs form the simple past in -ed; however there are a few hundred irregular verbs with different forms.
The term "simple" is used to distinguish the syntactical construction whose basic form uses the plain past tense alone, from other past tense constructions which use auxiliaries in combination with participles, such as the past perfect and past progressive.
Formation
Regular verbs form the simple past end-ed; however there are a few hundred irregular verbs with different forms. For details see.
Most verbs have a single form of the simple past, independent of the person or number of the subject (there is no addition of -s for the third person singular as in the simple present).
However, the copula verb be has two past tense forms: was for the first and third persons singular, and were in other instances.
The form were can also be used in place of was in conditional clauses and the like; for information on this, see subjunctive.
This is the only case in modern English where a distinction in form is made between the indicative and subjunctive moods in the past tense.
Questions, other clauses requiring inversion, negations with not, and emphatic forms of the simple past use the auxiliary did.
A full list of forms is given below, using the (regular) verb help as an example:
- Basic simple past:
- I/you/he/she/it/we/they helped
- Expanded (emphatic) simple past:
- I/you/he/she/it/we/they did help
- Question form:
- Did I/you/he/she/it/we/they help?
- Negative:
- I/you/he/she/it/we/they did not (didn't) help
- Negative question:
- Did I/you/he/she/it/we/they not help? / Didn't I/you/he/she/it/we/they help?
Usage
The simple past is used for a single event (or sequence of such events) in the past, and also for past habitual action:
- He took the money and ran.
- I visited them every day for a year.
It can also refer to a past state:
- I knew how to fight even as a child.
For action that was ongoing at the time referred to, the past progressive is generally used instead (e.g. I was cooking). The same can apply to states, if temporary (e.g. the ball was lying on the sidewalk), but some stative verbs do not generally use the progressive aspect at all, and in these cases the simple past is used even for a temporary state:
- The dog was in its kennel.
However, with verbs of sensing, it is common in such circumstances to use could see in place of saw, could hear in place of heard, etc.
- I felt cold.
If one action interrupts another, then it is usual for the interrupted (ongoing) action to be expressed with the past progressive, and the action that interrupted it to be in the simple past:
- Your mother called while you were cooking.
The simple past is often close in meaning to the present perfect.
The simple past is used when the event happened at a particular time in the past, or during a period which ended in the past (i.e. a period that does not last up until the present time).
This time frame may be explicitly stated, or implicit in the context (for example the past tense is often used when describing a sequence of past events).
- I was born in 1980.
- We turned the oven off two minutes ago.
- I came home at 6 o'clock.
- When did they get married?
- We wrote two letters this morning.
- She placed the letter on the table, sighed, and left the house.Contrast these examples with those given at.
Note also that for past actions that occurred before the relevant past time frame, the past perfect is used.
Various compound constructions exist for denoting past habitual action.
The sentence When I was young, I played football every Saturday might alternatively be phrased using used to (... I used to play ...) or using would (... I would play...).
The simple past also has some uses in which it does not refer to a past time.
- If he walked faster, he would get home earlier.
- I wish I knew what his name was.
These are generally in condition clauses and some other dependent clauses referring to hypothetical circumstances, as well as certain expressions of wish:
- He said he wanted to go on the slide.
Past Progressive
The past progressive or past continuous construction combines progressive aspect with past tense, and is formed using the past tense of be (was or were) with the present participle of the main verb.
It indicates an action that was ongoing at the past time being considered:
- At three o'clock yesterday, I was working in the garden. For stative verbs that do not use the progressive aspect, the simple past is used instead (At three o'clock yesterday we were in the garden).
The past progressive is often used to denote an action that was interrupted by an event, or for two actions taking place in parallel:
- While I was washing the dishes, I heard a loud noise.
- While you were washing the dishes, Sue was walking the dog.(Interrupted actions in the past can also sometimes be denoted using the past perfect progressive.)
The past progressive can also be used to refer to past action that occurred over a range of time and is viewed as an ongoing situation:
- I was working in the garden all day yesterday. That could also be expressed using the simple past, as I worked..., which implies that the action is viewed as a unitary event (although the effective meaning is not very different).
Past Perfect
The past perfect, sometimes called the pluperfect, combines past tense with perfect aspect; it is formed by combining had (the past tense of the auxiliary have) with the past participle of the main verb.
It is used when referring to an event that took place prior to the time frame being considered.
This time frame may be stated explicitly, as a stated time or the time of another past action:
- We had finished the job by 2 o'clock.
- He had already left when we arrived.
The time frame may also be understood implicitly from the previous or later context:
- I was eating ... I had invited Jim to the meal but he was unable to attend. (i.e. I invited him before I started eating)
- I had lost my way. (i.e. this happened prior to the time of the past events I am describing or am about to describe)
Compare He had left when we arrived (where his leaving preceded our arrival), with the form with the simple past, He left when we arrived (where his leaving was concurrent with or shortly after our arrival).
Note that unlike the present perfect, the past perfect can readily be used with an adverb specifying a past time frame for the occurrence.
For example, while it is incorrect to say I have done it last Friday (the use of last Friday, specifying the past time, would require the simple past rather than the present perfect), there is no such objection to a sentence like "I had done it the previous Friday".
The past perfect can also be used for states or repeated occurrences pertaining over a period up to a time in the past, particularly in stating "for how long" or since when". However, if the state is temporary and the verb can be used in the progressive aspect, the past perfect progressive would normally be used instead. Some examples with the plain past perfect:
- I had lived in that house for 10 years.
- The children had been in their room since lunchtime.
Past Perfect Progressive
The past perfect progressive or past perfect continuous (also known as the pluperfect progressive or pluperfect continuous) combines perfect progressive aspect with past tense.
It is formed by combining had (the past tense of auxiliary have), been (the past participle of be), and the present participle of the main verb.
Uses of the past perfect progressive are analogous to those of the present perfect progressive, except that the point of reference is in the past.
For example:
- I was tired because I had been running.
- By yesterday morning they had already been working for twelve hours.
- Among the witnesses was John Smith, who had been staying at the hotel since July 10.
This form is sometimes used for actions in the past that were interrupted by some event (compare the use of the past progressive as given above).
For example:
- I had been working on my novel when she entered the room to talk to me.
This implies that I stopped working when she came in (or had already stopped a short time before); the plain past progressive (I was working...) would not necessarily carry this implication.
If the verb in question does not use the progressive aspect, then the plain past perfect is used instead.
The past perfect progressive may also have additional specific uses similar to those of the plain past perfect.
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...).
B1 / Intermediate
A CEFR B1 level English language user is considered to be at an intermediate level. A B1 level English language user is expected to have the following abilities:
- Can understand sentences and frequently used expressions related to areas of most immediate relevance (e.g. very basic personal and family information, shopping, local geography, employment).
- Can communicate in simple and routine tasks requiring a simple and direct exchange of information on familiar and routine matters.
- Can describe in simple terms aspects of their background, immediate environment and matters in areas of immediate need.
- Can understand the main points of clear standard input on familiar matters regularly encountered in work, school, leisure, etc.
- Can produce simple connected text on topics that are familiar or of personal interest.
- Can describe experiences and events, dreams, hopes & ambitions and briefly give reasons and explanations for opinions and plans.
At B1 level, English language users are expected to have a basic level of proficiency in the language. They should be able to understand and produce language in simple and routine tasks, and be able to communicate in familiar and routine matters. They should be able to understand the main points of clear standard input on familiar matters and be able to produce simple connected text on topics that are familiar or of personal interest. They are able to express themselves with a degree of fluency, but with some hesitation, and occasional errors in grammar and vocabulary.
Difficulty: Easy
Easy difficulty. Difficulty levels represent author's opinion about how hard a question or challenge is.