The correct answers are not be left and should not be left.
In formal English, verbs like demand, insist, and recommend trigger the mandative subjunctive in the following that-clause.
To form the negative passive subjunctive, we simply use not + be + past participle (e.g., not be left). We do not use "do/does" as an auxiliary verb in the subjunctive mood.
Using should + base verb (e.g., should not be left) is also perfectly correct and is especially common in British English as an alternative to the pure subjunctive.
Subjunctive mood
If you've heard if I were you and wondered why it's not if I was you — you've met the past subjunctive. English barely marks the subjunctive anymore, but in formal writing and a few stock phrases, getting it right (or wrong) is one of the clearest signals of a careful writer. I demand that he be present. / If I were richer. — both subjunctive, both reading as wrong if you swap them out.
The subjunctive mood marks hypothetical or counterfactual contexts. Two main forms: present subjunctive in that-clauses after verbs of recommendation (I suggest that he go) and past subjunctive were in unreal conditionals (If I were you). Mostly invisible in modern English, but unmistakable when present.
Passive voice
If your writing has been called "weak" or "evasive" — Mistakes were made, It was decided that... — you've hit the passive voice's main pitfall. Used deliberately, the passive is precise and useful: it foregrounds the action when the doer doesn't matter. Used by default, it makes prose feel like nobody's responsible for anything.
The passive voice is formed with be + past participle and turns the object into the subject: The chef cooked the meal → The meal was cooked (by the chef). Useful when the action matters more than the doer; overused, it makes writing feel evasive.
Negation
If your native language uses double negatives (I don't see nothing) — like Russian, Spanish, or French — you've probably been told this is wrong in English and not been entirely sure what the fix is. Standard English uses one negative per clause: either I saw nothing or I didn't see anything, never both. Once you internalise that single rule, your written English clears up a lot.
Negation in English uses not after an auxiliary or modal verb: I am not going. Without an auxiliary, you add do-support (I do not go). Negative words like never and nobody already negate the clause — adding not on top creates non-standard double negatives.
Verb mood
If grammar references confuse you with terms like "subjunctive" or "conditional" — and you've never quite understood why English needs them — you've hit the verb-mood layer. Each mood marks a different attitude: fact vs command vs hypothetical vs polite recommendation. Once that map is clear, structures like if I were you or I suggest he go stop looking like exceptions and start looking like a system.
Verb mood signals the speaker's attitude toward the action. The four English moods: indicative (facts), imperative (commands), subjunctive (hypotheticals, formal recommendations), and conditional (would/could constructions).
Clause
If you've ever been told your sentence is a "run-on" or that you've used a comma where there should be a semicolon — you've hit the limits of writing without seeing clauses. Get this concept solid and most punctuation problems quietly disappear: you can finally tell a complete thought from a fragment without guessing.
A clause is a grammatical unit built around a verb, usually with a subject and a predicate. Independent clauses stand alone (I missed the bus); dependent clauses can't (Because I overslept). Combine them and you build complex sentences.
C1 | Advanced
If you've ever sat through a lecture in English, written a complaint letter, or argued a point in a meeting and come out feeling actually understood — not just tolerated — you've felt what C1 looks like. The level matters because it's where most universities, certifications, and skilled-work environments draw their language line.
C1 is the advanced level in the CEFR framework, demanding fluent and flexible language: inversion for emphasis, mixed and advanced conditionals, formal subjunctive, cleft sentences, and complex nominal phrases — all used appropriately across registers.
Difficulty: Hard
If easy and medium questions are clicking but you still feel exposed in real conversation or formal writing, you've outgrown the basics. Hard material is where the gaps you didn't know you had show up: the distractor that "sounds right", the rule that interacts with another rule, the case where context changes the answer. It's where genuine fluency is built.
The Hard difficulty tag marks upper-intermediate to advanced challenges — typically B2 and above. Interacting rules, edge cases, plausible distractors, and contexts that require genuine understanding rather than surface pattern-matching.