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Help the ambitious science student explain her highly unusual experiment to her skeptical professor by choosing the correct prepositions.
"Professor, I must insist _________________________ conducting this experiment with the radioactive hamsters. My entire thesis depends _________________________ their ability to run in the wheel at light speed. I know you object _________________________ the potential danger, but I believe _________________________ my safety protocols!"

The correct prepositions are on, on, to, and in.

We say insist on doing something. Things depend on other things (never depend of or depend from). You object to an idea or action. You believe in something when you trust its value or existence.

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Collocations

Collocations are combinations of words that frequently occur together in a specific order, creating a natural-sounding expression in a given language. These word pairs or groups are more likely to be used by native speakers than other possible combinations of the same words. A thorough understanding of collocations is crucial for language learners, as it enhances fluency and allows for more natural speech and writing.

There are several types of collocations, including:

  1. Verb + Noun: In this type of collocation, a verb is paired with a noun to create a specific meaning. Examples include "make a decision," "take a shower," and "perform an operation."
  2. Adjective + Noun: This collocation type combines an adjective with a noun to describe a particular quality or characteristic. Examples include "strong coffee," "heavy rain," and "bright future."
  3. Noun + Noun: In this collocation, two nouns are combined to create a compound noun, such as "kitchen table," "traffic jam," and "school bus."
  4. Adverb + Adjective: This type of collocation pairs an adverb with an adjective to provide more detail or emphasis. Examples include "highly unlikely," "deeply concerned," and "fully aware."
  5. Adverb + Verb: In this collocation, an adverb is used to modify a verb, such as "strongly believe," "quickly run," and "patiently wait."
  6. Verb + Adverb: This type of collocation combines a verb with an adverb to describe the manner in which an action is performed. Examples include "speak softly," "work diligently," and "think critically."

Understanding and using collocations effectively can greatly improve a language learner's ability to communicate naturally and accurately. Recognizing these common word combinations is essential for developing fluency and enhancing comprehension in both spoken and written language.

English Grammar

English grammar is the way in which meanings are encoded into wordings in the English language. This includes the structure of words, phrases, clauses, and sentences, right up to the structure of whole texts.

Humor

Humor is subjective, but at least the author tried.

Preposition

Prepositions form a closed word class, although there are also certain phrases that serve as prepositions, such as in front of.

A single preposition may have a variety of meanings, often including temporal, spatial and abstract. Many words that are prepositions can also serve as adverbs. Examples of common English prepositions (including phrasal instances) are of, in, on, over, under, to, from, with, in front of, behind, opposite, by, before, after, during, through, in spite of or despite, between, among, etc.

A preposition is usually used with a noun phrase as its complement.

A preposition together with its complement is called a prepositional phrase.

Examples are in England, under the table, after six pleasant weeks, between the land and the sea.

A prepositional phrase can be used as a complement or post-modifier of a noun in a noun phrase, as in the man in the car, the start of the fight; as a complement of a verb or adjective, as in deal with the problem, proud of oneself; or generally as an adverb phrase.

English allows the use of "stranded" prepositions. This can occur in interrogative and relative clauses, where the interrogative or relative pronoun that is the preposition's complement is moved to the start (fronted), leaving the preposition in place. This kind of structure is avoided in some kinds of formal English.

For example:

  • What are you talking about? (Possible alternative version: About what are you talking?)
  • The song that you were listening to ... (more formal: The song to which you were listening ...)

Notice that in the second example the relative pronoun that could be omitted.

Stranded prepositions can also arise in passive voice constructions and other uses of passive past participial phrases, where the complement in a prepositional phrase can become zero in the same way that a verb's direct object would: it was looked at; I will be operated on; get your teeth seen to.

The same can happen in certain uses of infinitive phrases: he is nice to talk to; this is the page to make copies of.

Verb

A verb is a word that expresses an action, a state, or an occurrence — and it's the engine of every English sentence. Understanding how verbs work is foundational to everything else in English grammar, from forming questions to building complex sentences.

Verb Forms

Most English verbs have five inflected forms:

  • Base form (go, write, climb) — used as an infinitive, imperative, present subjunctive, and present indicative in all persons except third-person singular.
  • -s form (goes, writes, climbs) — used for the present tense, third-person singular (she writes).
  • Past tense (went, wrote, climbed) — also called the preterite.
  • Past participle (gone, written, climbed) — identical to the past tense for regular verbs, but often different for irregular verbs.
  • -ing form (going, writing, climbing) — serves as the present participle and gerund.

The verb be is a special case with more forms than any other English verb (am, is, are, was, were, been, being). Modal verbs like can, must, and should have fewer forms than typical verbs.

Main Verbs and Auxiliaries

Verbs in English often appear in combinations: one or more auxiliary verbs paired with a main verb.

  • The dog was barking very loudly.
  • My hat has been cleaned.
  • Jane does not really like us.

The first verb in the combination is the finite verb (it carries tense and agrees with the subject). The rest are nonfinite (infinitives or participles). Notice that these verbs don't always sit next to each other — as in does not really like.

Tense, Aspect, and Mood

English expresses tense (time reference), aspect (how an action unfolds over time), and mood (the speaker's attitude toward the action) mostly through verb combinations rather than word endings. That's why you'll encounter labels like "present progressive" or "conditional perfect" — these are specific tense–aspect–mood combinations built with auxiliaries.

Self-check: If you can change the time of a sentence by swapping one word (She runs → She ran), that word is the verb.

Keep Practising

To build your verb skills from the ground up, try these challenges: Basics. "To be" in Present Tense, Basics. Common Uses of Auxiliary Verbs, and Transitive and Intransitive Verbs.

B2 | Upper Intermediate

B2, or Upper Intermediate, is the fourth level on the CEFR scale. It marks the point where you move from "getting by" to genuinely comfortable communication — handling complex topics, expressing nuanced opinions, and understanding most of what you read or hear in real-world contexts.

What a B2 user can do

At this level, you're expected to:

  • Understand complex texts on both concrete and abstract topics, including technical discussions in your own field.
  • Follow extended speech and lectures, even when the structure isn't entirely clear, as long as the topic is reasonably familiar.
  • Interact fluently and spontaneously enough that conversations with native speakers flow naturally — without strain on either side.
  • Produce clear, detailed text on a wide range of subjects, using connectors and cohesive devices to build well-structured arguments.
  • Explain and defend a viewpoint on a topical issue, weighing the advantages and disadvantages of different options.
  • Recognize implicit meaning — reading between the lines in demanding, longer texts.

What B2 grammar looks like in practice

B2 is where grammar stops being about isolated rules and starts being about flexibility and precision. You're expected to control structures like:

  • Advanced conditionals and mixed conditionals — moving beyond simple if-clauses to express hypothetical and counterfactual meaning.
  • Passive voice in varied tenses and contexts, not just present and past simple.
  • Reported speech with correct sequence of tenses, including backshifting and reporting verbs.
  • Participle clauses and the distinction between participles and gerunds.
  • Comparative and superlative structures beyond basic -er/-est, including double comparatives and qualifying expressions.

Errors still happen at B2, but they rarely cause misunderstanding. The goal is controlled, flexible use of language across social, academic, and professional settings.

How B2 fits in the CEFR progression

B2 builds directly on the foundations of B1 (Intermediate) and prepares you for C1 (Advanced). Many university entrance exams, professional certifications, and immigration requirements target B2 as the minimum standard.

Self-check: If you can read a newspaper editorial, follow most of a TED talk without subtitles, and write a clear essay arguing a position — you're likely operating at B2.

Ready to test yourself? Try Is your English level B2/Upper Intermediate? or practise specific B2 grammar with challenges like Basics. Advanced Conditionals And "wish", Basics. Passive Voice, and Sequence of Tenses in Indirect Speech.

Difficulty: Medium

Medium difficulty. Difficulty levels represent author's opinion about how hard a question or challenge is.