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
Must vs should vs might: the most confused modal trio. Must = strong obligation/near-certainty. Should = advice/expectation. Might = possibility. Getting these wrong changes the force of your statement: You must see a doctor (urgent) vs You should see a doctor (advice) vs You might need a doctor (maybe).
Modal verbs are auxiliaries that encode modality: ability (can), permission (may), necessity (must), advice (should), possibility (might), future (will).
Diagnostic: what meaning are you adding? Obligation → must/have to. Advice → should. Possibility → might/could. Ability → can. Future → will.
Grammatical number
Subject-verb agreement: the verb must match the subject's number, not the nearest noun. The list of items is long (✅) — not are, because the subject is list (singular), not items. This "attraction" error is the most common number mistake.
Grammatical number is the singular/plural system affecting nouns, pronouns, and verbs. Agreement means making them all match.
Diagnostic: find the actual subject (ignore prepositional phrases between subject and verb). Is it singular or plural? Match the verb to that.
Subject
Subject vs object: the subject does or is; the object receives. She (subject) hit him (object). In English, position decides: subject comes before the verb, object after. Unlike inflected languages, English rarely marks subjects with case (exception: pronouns — I vs me).
The subject = who/what the sentence is about. Controls verb agreement. Usually a noun/pronoun before the verb.
Diagnostic: ask "who or what [verb]s?" The answer is the subject. The list of items is wrong — what is wrong? The list. That's your subject.
English grammar
Grammar vs vocabulary: vocabulary gives you the words; grammar gives you the system for combining them into meaning. Knowing 10,000 words without grammar produces incoherent sentences. Knowing grammar with limited vocabulary produces clear, correct sentences about fewer topics. Both matter — but grammar is the framework.
English grammar is the complete rule system: parts of speech, phrase and sentence structure, tenses, agreement, word order, and punctuation.
Diagnostic: if your sentences are understood but "sound wrong" → grammar issue. If you can't find the right word → vocabulary issue. If both → start with grammar.
A2 | Elementary | Pre-intermediate
A2 vs B1: A2 handles routine transactions and simple past narration. B1 handles connected discourse, explaining reasons, and understanding main points in clear standard speech. If you can tell what happened but not why it matters, you're still A2.
A2 is the elementary level of the CEFR: past simple, present perfect, first conditional, basic modals, and routine communication about familiar topics.
Diagnostic: can you link ideas with because, although, so that and hold a conversation beyond scripted topics? No → A2. Yes → moving into B1.
Easy
Easy vs Medium vs Hard: Easy = one rule, obvious answer, A1–A2. Medium = one rule but realistic distractors, A2–B1. Hard = interacting rules, edge cases, B2+. Start Easy to check you have the basics before moving up.
The Easy tag filters for single-rule, short-sentence, common-vocabulary challenges designed for beginners or for anyone wanting a confidence check on fundamentals.
Diagnostic: if you get Easy questions wrong, stay here — your foundations need work. If they feel trivial, move to Medium.