Help the anxious museum curator finalize the security checklist for the new diamond exhibit by dragging the correct phrases into the blanks.
The famous diamond must not be touched by anyone under any circumstances. To ensure maximum safety, all security cameras should be checked every hour before the doors open. Finally, the emergency alarms can be activated remotely if there's even the slightest hint of trouble.
The famous diamond must not be touched by anyone under any circumstances.
We form the passive voice with modal verbs using modal + be + past participle. Here, "must not be touched" shows that touching the diamond is strictly prohibited.
To ensure maximum safety, all security cameras should be checked every hour before the doors open.
"Should be checked" is the correct passive form to express a strong recommendation or requirement.
Finally, the emergency alarms can be activated remotely if there's even the slightest hint of trouble.
"Can be activated" shows that it is possible for the alarms to be triggered by someone remotely.
Passive voice
Active vs passive: active puts the doer first (The dog bit the man). Passive puts the receiver first (The man was bitten by the dog). Neither is inherently wrong — choice depends on what you want to foreground. Scientific/formal writing uses passive deliberately; vague writing uses it accidentally.
Passive voice = be + past participle. Promotes the object to subject. Good for foregrounding the action/result; bad when it hides who's responsible.
Diagnostic: who's doing the action? If unnamed and that matters → bad passive. If unnamed because it's obvious or irrelevant (The building was constructed in 1920) → good passive.
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.
Verb
Verb vs noun vs adjective: nouns name things. Adjectives describe. Verbs express what happens or what IS. The test: can it take tense (walked, will walk)? Can it take -ing? Can it follow to as an infinitive (to walk)? Yes to any → verb. English often converts freely between classes (run = noun or verb), so context decides.
A verb = action/state/occurrence word. 5 forms (base, -s, past, past participle, -ing). Carries tense, aspect, mood, voice. The one required element in every sentence.
Diagnostic: does it change for tense (walk → walked)? Can you put to before it (to walk)? Does it take -ing (walking)? → verb.
Negation
Single vs double negatives: standard English uses ONE negative per clause (I don't see anything or I see nothing). Double negatives (I don't see nothing) are grammatical in many languages and some English dialects, but are non-standard in written/formal English. This is the #1 negation trap for speakers of Spanish, Russian, and French.
Negation = not after auxiliary/modal, or do-support. Negative words (never, nobody, nothing) negate alone without adding not.
Diagnostic: count the negatives in the clause. More than one? → double negative. Fix by replacing one with a positive (anything, anyone, ever).
B1 | Intermediate
B1 vs B2: B1 handles standard everyday communication and simple opinions. B2 handles abstract topics, sustained arguments, and nuanced register. If you can chat about your life but struggle to debate an issue or write a formal essay, you're B1.
B1 is the intermediate CEFR level: independent handling of familiar topics, second conditional, basic passive, reported speech, and linking words for cause and contrast.
Diagnostic: can you read a newspaper article on a familiar topic and summarise the argument? Comfortably → B2. Struggle with abstractions → still B1.
Medium
Medium vs Easy: Easy has one obviously correct answer and clearly wrong distractors. Medium has one correct answer but plausible distractors — you need to actually know the rule, not just guess from sound.
The Medium tag filters for A2–B1 challenges with realistic difficulty: one rule per question, plausible alternatives, everyday contexts.
Diagnostic: if you're scoring 90%+ on Easy, move here. If you're below 60% on Medium, go back to Easy for that topic. Target 70–80% accuracy for maximum learning.