After the present simple form are, we can only follow to with the infinitive: to buy.
Modal verb
A modal verb is a special class of auxiliary — can, could, may, might, must, shall, should, will, would — that adds shades of meaning around possibility, ability, permission, obligation, or speculation. I can swim (ability), You should rest (advice), It might rain (possibility), You must leave (obligation).
Modals are grammatically peculiar: no -s in the third person (she can, not she cans), no infinitive, no participle, followed by the bare verb (I can swim, never I can to swim). Mastering them is the move from describing facts to expressing how you feel about them — likelihood, necessity, recommendation.
Auxiliary verb
An auxiliary verb (or "helping verb") is a verb that combines with a main verb to add grammatical meaning — questions, negation, tense, aspect, voice, or modality. The English auxiliaries are forms of be, have, do, plus the modal verbs (can, could, will, would, should, may, might, must).
Auxiliaries are what let you build past tense (have gone), continuous aspect (is going), passive voice (was eaten), and questions (Do you know?). Without them, you can't form most of the structures you need beyond the simple present and past — they're the engine that powers half the tense system.
Conditional sentence
A conditional sentence describes one situation as depending on another. It pairs a condition clause (usually starting with if) with a consequence clause: If it rains, we'll stay in. The condition can refer to general truths, real future possibilities, hypothetical present situations, or unreal past situations — and each type uses a specific tense pattern.
English teaching groups these into zero, first, second, third, and mixed conditionals. Mastering them lets you talk about plans, regrets, hypotheticals, and warnings — territory you can't reach with simple present and past tenses alone.
Idiom
An idiom is a fixed expression whose meaning isn't predictable from the words it contains. Kick the bucket doesn't mean physically kicking a bucket — it means to die. Spill the beans means to reveal a secret. It's raining cats and dogs means it's pouring rain. The cultural meaning has fully replaced the literal one.
English is dense with idioms, and recognising them is the difference between feeling lost in a casual conversation and following along easily. They can't usually be translated word-for-word into other languages — they have to be learned as whole units, like vocabulary.
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.