The secret sauce must be kept in the fridge at all times. Please remember that the fancy gold-rimmed plates should not be washed in the dishwasher, or they will lose their sparkle!
To form the passive voice with a modal verb, use modal + be + past participle.
The sauce doesn't keep itself; it must be kept by someone.
The plates don't wash themselves; they should not be washed by someone.
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.
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.
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.
B1 | Intermediate
B1 is the intermediate level in the CEFR framework — the point where you stop relying on memorised phrases and start handling everyday English independently. At B1 you can describe experiences, explain opinions, and follow most clear standard speech on familiar topics like work, travel, and hobbies.
Grammatically, B1 means combining tenses with precision, building complex sentences, and starting to use passive voice, modal verbs for necessity and possibility, and verb patterns (gerund vs. infinitive). Knowing your level shapes what you study next: pushing too far ahead frustrates you; staying below your level wastes time.
Difficulty: Medium
The Medium difficulty tag marks questions and challenges in the middle of the difficulty range — typically suitable for A2 to B1 learners. Expect a single rule with realistic distractors, longer sentences, and contexts where you have to think before answering rather than reading off the obvious choice.
Filter by Medium when you're past the absolute basics and ready to consolidate. It's the level where most lasting progress happens — easy enough that you can finish without exhausting concentration, hard enough that getting it right means you've actually understood.