Complete the frustrated traveler's diary entry.
The passengers _____ stranded at the airport for over twelve hours finally received a half-hearted apology and a single stale donut.
The correct answer is left.
This is a passive reduced relative clause. The full clause would be "who were left stranded." To reduce it, we remove the relative pronoun ("who") and the "be" verb ("were"), leaving only the past participle left.
"Leaving" would incorrectly imply the passengers were doing the action of leaving someone else. "Were left" creates a grammar error because the sentence already has a main verb ("received").
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.
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.