The waiters dropping plates every five minutes didn't seem to care about the noise.
Use the present participle (-ing) to reduce an active relative clause ("waiters who were dropping plates"). Using the past tense "dropped" here would create a grammatically incorrect run-on sentence.
The soup, served at absolute zero, was ironically the highlight of the meal.
Use the past participle to reduce a passive relative clause ("soup which was served").
I believe I was the only patron to survive the evening without getting food poisoning!
When a noun is modified by phrases like "the first," "the last," or "the only," we use a to-infinitive to reduce the relative clause ("the only patron who survived").
Relative clause
A relative clause is a dependent clause that modifies a noun, typically introduced by a relative pronoun (who, whom, whose, which, that) or relative adverb (where, when, why). The man who lives in this house has not been seen for days. They split into restrictive (essential to the meaning, no commas) and non-restrictive (extra information, set off by commas).
The split matters because the comma changes the meaning: My brother who lives in Paris (one of several brothers) vs. My brother, who lives in Paris, (my only brother). Getting comma placement right is one of the highest-leverage moves at B2+.
Participle
A participle is a verb form that doubles as an adjective or adverb. English has two: the present participle ending in -ing (running, sitting) and the past participle (broken, gone, written). Both build tenses (is running, has gone), but they also stand alone modifying nouns (the broken window) or verbs (Exhausted, we fell asleep).
Participles look like simple parts of speech but pull double duty — most learner errors come from confusing the present participle with the gerund (also -ing but acting as a noun) or the past participle with the past tense.
Infinitive
The infinitive is the basic, unmarked form of a verb, used when no tense or subject agreement is needed. English has two flavours: the to-infinitive (to swim, to read) and the bare infinitive (swim, read). The to-infinitive follows verbs like want, decide, hope, plan (I want to swim); the bare infinitive follows modal verbs (I can swim) and certain causative verbs (Let him go).
Knowing which form to use after which verb is one of the trickiest distinctions in English — closely tied to the parallel choice of gerund (-ing form). I want to swim but I enjoy swimming aren't interchangeable.
Clause
A clause is a grammatical unit built around a verb — typically a subject plus a predicate (She laughed; The manager approved the budget). Clauses come in two types: independent clauses stand alone as complete sentences; dependent clauses need an independent clause to make sense (Because I overslept — incomplete on its own).
Spotting clause boundaries is the foundation of correct punctuation. Once you can see where one clause ends and another begins, comma rules, run-on sentences, and complex sentence structure stop being mysteries.
Passive voice
The passive voice flips a sentence so the object of the action becomes the subject, and the original doer either disappears or moves to a by-phrase: The chef cooked the meal (active) → The meal was cooked by the chef (passive). Formed with be + past participle (was cooked, is being written, had been seen), and works across all tenses.
Use the passive when the action matters more than the doer (The report was filed), when the doer is unknown or obvious (My car was stolen), or to soften criticism (Mistakes were made). Overusing it makes prose feel evasive — careful writers reach for the active voice by default.
B2 | Upper Intermediate
B2 is the upper-intermediate level in the CEFR framework, sitting between B1 and C1. At B2 you can read editorials, follow most TED talks without subtitles, and hold extended conversations on abstract topics — including topics outside your everyday life.
Grammatically, B2 means flexible control of mixed conditionals, passive voice across tenses, reported speech with proper backshifting, and participle clauses. B2 is the standard target for university entrance exams (IELTS 5.5–6.5, TOEFL 87–109) and most skilled-migration thresholds — knowing whether you're there shapes your study plan.
Difficulty: Hard
The Hard difficulty tag marks questions and challenges aimed at upper-intermediate to advanced learners — typically B2 and above. Expect interacting rules, edge cases, distractors that look right at first glance, and contexts where the surface meaning and the grammatical answer don't match.
Filter by Hard when you're past the basics and want material that genuinely tests your understanding. These questions catch the gaps your textbook didn't — register-sensitive choices, exception cases, mixed conditionals, the difference between would have been and had been.