The correct answers are must and has to.
"Each student" is a singular subject (he/she/they).
We use the singular form has to instead of "have to".
Must is a modal verb, which means its form never changes regardless of the subject (so "musts" is not a real word!). Both correct options express a strong obligation or rule.
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.
Grammatical number
If you've ever written The data shows and been told it should be The data show — or written The list of items are when it should be is — you've hit a grammatical-number trap. Number agreement looks simple in theory (one takes singular, more than one takes plural) but English has enough irregular plurals and tricky collective nouns to keep you on your toes.
Grammatical number is the singular/plural distinction on nouns, pronouns, and verbs. Most English nouns form plurals with -(e)s; pronouns have irregular pairs (I/we, he/they); verbs agree with their subject (He goes vs They go).
Subject
If you've ever written The list of items are wrong (should be is wrong) — you've hit the subject-agreement trap. The subject is list, not items, and the verb has to agree with it. Long sentences with prepositional phrases between the subject and verb are where this most often goes wrong, and getting it right is what stops careful readers from flagging your writing.
The subject is the part of a sentence or clause that says who or what the sentence is about. Typically a noun, pronoun, or noun phrase before the verb, controlling the verb's number and person.
English grammar
If you can speak English but feel you're forever guessing — should that be a/the?, would have been or had been?, who or whom? — you don't have a vocabulary problem; you have a grammar problem. Grammar is the system that turns isolated words into precise meaning, and the only difference between guessing and knowing is studying it deliberately.
English grammar is the system of rules that govern how meanings are encoded in English: word formation, phrase and sentence structure, tenses, agreement, word order, and punctuation.
A2 | Elementary | Pre-intermediate
If you can order coffee, ask for directions, and tell someone what you did yesterday — but struggle the moment the conversation drifts into anything abstract — you're operating at A2. Knowing this matters: A2 is the level where most learners plateau because they reach for B2 material too early and burn out. Stay here and your foundations get unbreakable.
A2 is the elementary level in the CEFR framework, covering routine communication and the first wave of real grammar: past simple and continuous, present perfect, basic modal verbs, first conditional, and common verb-pattern rules.
Difficulty: Easy
If a textbook leaves you confused, sometimes the issue isn't the topic — it's that the practice material is layered with extra complications. Filtering by Easy strips that away. You get one rule at a time, in plain everyday language, with no trick questions. It's how you make a shaky foundation solid before stacking more on top.
The Easy difficulty tag marks beginner-level questions and challenges — typically A1 or early A2. Single-rule focus, short sentences, common vocabulary, one clear correct answer.