Help the secret agent understand the rather alarming warning label on his new spy car. Choose the correct phrase to complete the sentence.
"You can deploy the oil slick whenever you like, but you ______ press the big red button, or the car will instantly self-destruct!"
The correct answer is mustn't.
We use mustn't (must not) to express a strong prohibition—it means "do not do this" or "it is forbidden."
Don't have to means something is optional (you can do it if you want, but it's not required), which would be a terrible instruction for a self-destruct button!
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.
English Grammar Basics
If grammar feels like a tangle of rules you can never quite remember, the fix isn't more advanced material — it's making the foundations automatic. The English Grammar Basics tag is where you do that: the building blocks every other topic stands on. Get these right and the rest stops feeling random.
It marks quizzes and explainers covering the core of English: nouns, verbs, adjectives, adverbs, prepositions, conjunctions, tenses, voice, mood, and basic sentence structure. Useful whether you're a beginner or refreshing rusty knowledge.
Humor
If you've ever reached the third drill of present perfect and felt your eyes glaze over, you've hit the limits of dry repetition. Practice that's even mildly funny is far easier to come back to — and far easier to remember weeks later. That's the whole point of the Humor tag.
The Humor tag marks questions where the author has tried to make the practice entertaining alongside instructive. Subjective, sometimes silly, but designed to keep you engaged long enough for the rule to stick.
B1 | Intermediate
If you can hold a conversation about your weekend, explain why you're late, and follow a short news story without panicking — but still feel lost in fast or technical English — you're probably operating at B1. Knowing this matters: study material at the wrong level either bores you or burns you out, and B1 is the typical target for travel, casual work, and most everyday social English.
B1 is the intermediate level in the CEFR framework, where you handle everyday English independently and start combining ideas with complex sentences, passive voice, and modal verbs.
Difficulty: Medium
If easy questions feel too obvious but hard questions leave you guessing, you're probably ready for Medium — the level where most real learning happens. It pushes just enough to expose the rules you don't quite have yet, without burying you in edge cases. This is where steady fluency is built, one well-aimed challenge at a time.
The Medium difficulty tag marks middle-range challenges — typically A2 to B1. One rule per question, realistic distractors, and contexts that require active thought rather than instant recognition.