Help Dr. Von Quark finalize the safety protocols for his new time machine by dragging the correct verb forms into the gaps.
It is imperative that the temporal capacitor remain completely submerged in pickle juice.
I strongly recommend that my assistant, Igor, be wearing his lead underwear when the countdown begins.
Furthermore, I dictate that the dimensional portal not be opened until after lunch.
It is imperative that the temporal capacitor remain completely submerged in pickle juice.
Adjectives expressing urgency or necessity (like "imperative") trigger the subjunctive in the following that-clause. We use the base form of the verb ("remain") without an "-s".
I strongly recommend that my assistant, Igor, be wearing his lead underwear when the countdown begins.
Verbs of recommending trigger the subjunctive. Here, we need the continuous subjunctive form, which is "be" + present participle ("be wearing").
Furthermore, I dictate that the dimensional portal not be opened until after lunch.
This gap requires both the negative and passive subjunctive. We place "not" before the base form "be", followed by the past participle "opened".
Subjunctive mood
The subjunctive mood is the verb form English uses for hypothetical, counterfactual, or formal-recommendation contexts. The two main patterns are: the present subjunctive in that-clauses after verbs of recommendation/insistence (I suggest that he go, It's essential that she be informed), and the past subjunctive were in counterfactual conditionals (If I were you).
Most subjunctive forms in modern English look identical to the indicative — the visible signs are the missing third-person -s (he go, not he goes) and were with first/third-person singular (if I were). Easy to miss; a strong marker of careful, formal English when used.
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.
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.
Negation
Negation in English usually places not after the auxiliary or modal verb: I am not going, She does not know, You must not go. When there's no auxiliary, you add do-support: I go → I do not go. Most combinations contract: don't, can't, won't, isn't.
The trickiest rule for many learners: double negatives are not standard English. I didn't see nothing is non-standard; the standard forms are I saw nothing or I didn't see anything. Negative words like never, nobody, nothing already carry the negation — adding not on top doubles up.
Verb
A verb is a word that expresses an action, a state, or an occurrence — the engine of every English sentence. Most verbs have five forms: base (go), -s form (goes), past tense (went), past participle (gone), and -ing form (going). The verb be is the major exception with eight forms; modal verbs like can and must have fewer.
Verbs carry tense (when), aspect (how it unfolds), mood (the speaker's attitude), and voice (active vs passive). Mastering them is foundational — virtually every other grammar topic depends on getting verbs right.
C1 | Advanced
C1 is the advanced level in the CEFR framework, sitting between B2 and C2. At C1 you stop translating in your head and start thinking in English — handling specialised articles outside your field, picking up implicit meaning, and writing structured arguments on complex topics.
Grammatically, C1 means natural use of inversion (Rarely have I seen…), mixed and advanced conditionals, subjunctive forms in formal contexts, and cleft sentences for emphasis. Most university programmes for non-native speakers and many professional certifications set C1 as their entry standard.
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.