Select correct verbs.
If Paula could go back in time, she wouldask Boris to marry her.
If Paula could go back in time, she would ask Boris to marry her.
Could is often used in sentences with unreal conditions: going back in time is impossible.
If Paula could go back in time, she would ask Boris to marry her.
would + simple infinitive is used as the outcome is completely unrealistic.
If Paula could go back in time, she would ask Boris to marry her.
The main clause in the second type conditional is formed by would + simple infinitive, in this case ask
Conditional sentence
Want to say I would have caught the train if I'd left earlier without freezing on the verb forms? That's a third conditional, and it's one of five patterns English uses to talk about possibilities, regrets, and hypotheticals. Get the system right and you stop sounding stuck in the present tense.
A conditional sentence pairs a condition clause (usually with if) with a consequence clause: If it rains, we stay in. The five named patterns — zero, first, second, third, and mixed — each match a specific time frame and likelihood, with their own tense rules.
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.
Auxiliary verb
If you've ever wondered why English asks Do you know? instead of Know you?, or how a single sentence can carry tense, aspect, AND voice (has been being cleaned), you've felt the work of auxiliary verbs. They're tiny words that quietly carry most of English's grammatical machinery — get them wrong and questions, negatives, and tenses all fall apart.
An auxiliary verb combines with a main verb to add grammatical meaning. The English auxiliaries are be, have, do, and the modal verbs (can, will, should…). They handle questions (Do you?), negation (don't), tense and aspect (has gone, is going), and passive voice (was eaten).
Modal verb
If you've ever struggled with the difference between You must do this (strong command) and You should do this (advice) — or It might rain (possible) and It will rain (certain) — you've felt how much modal verbs do in English. They're how the language signals certainty, obligation, possibility, and politeness, and getting them right is what stops your speech from sounding either pushy or wishy-washy.
A modal verb is an auxiliary — can, could, may, might, must, shall, should, will, would — adding meaning around ability, permission, possibility, obligation, or speculation. Always followed by the bare infinitive (can swim, never can to swim), and never inflected for person.
Verb tense
If you've ever frozen mid-sentence wondering whether to say I worked or I have worked, I had been doing or I was doing — you've felt the weight of English's tense system. Twelve forms, each with a specific job, and the wrong choice subtly misrepresents your meaning. Mastering tenses is the longest single project in English grammar, but it's also the one with the biggest payoff.
Verb tense signals when an action happens. English has three time references (past, present, future) combined with three aspects (simple, progressive, perfect), giving twelve standard forms. Each carries a specific meaning beyond just timing.
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.