Choose the correct option to complete this tense corporate boardroom email.
If the board of directors won't hold the CEO accountable, then the shareholders _____.
The correct answer is must.
This sentence uses Verb Phrase Ellipsis. Instead of repeating the entire phrase "hold the CEO accountable," we can drop it entirely and just use the modal verb "must" to stand in for the whole idea.
"Must hold" is grammatically incorrect here because "hold" is a transitive verb and requires an object immediately after it. "Must do" and "must have" use the wrong auxiliary verbs for this context.
Modal verb
- ✅ She can swim. — ❌ She can to swim. (modal + bare infinitive, no to)
- ✅ You must leave now. — strong obligation
- ✅ It might rain. — possibility (~50%)
- ✅ He should apologise. — advice/recommendation
Modal verbs (can, could, may, might, must, shall, should, will, would) are auxiliaries expressing ability, permission, possibility, obligation, or speculation. Always + bare infinitive. Never inflected (she can, not she cans).
Rule: modals never take to after them, never add -s for third person, and can't combine directly (must can ❌ — use must be able to).
Conditional sentence
- ✅ If you heat ice, it melts. — zero conditional (always true)
- ✅ If it rains, I*'ll** take an umbrella.* — first conditional (real future)
- ✅ If I had wings, I would fly. — second conditional (unreal present)
- ✅ If I had left earlier, I would have caught the train. — third conditional (unreal past)
Conditional sentences pair an if-clause with a consequence. Five patterns (zero through mixed) each combine specific tenses to express different levels of reality and time.
Pattern: the tense in the if-clause is always one step "back" from what you'd expect — past for present hypotheticals, past perfect for past hypotheticals.
Auxiliary verb
- ✅ Do you know? — ❌ Know you? (English requires do-support for questions)
- ✅ She has finished. — ❌ She finished has. (auxiliary before main verb)
- ✅ They are leaving. — ❌ They leaving. (progressive needs be)
- ✅ He doesn't smoke. — ❌ He smokes not. (negation needs do)
Auxiliary verbs (be, have, do, and the modals) combine with main verbs to build questions, negatives, tenses, aspects, and passive voice.
Pattern: if you need to ask a question, negate, or stack tense/aspect — you need an auxiliary. The main verb carries meaning; the auxiliary carries grammar.
C1 | Advanced
- ✅ Not only did she finish early, but she also helped others. — inversion for emphasis
- ✅ It is the process that matters, not the result. — cleft sentence
- ✅ I insist that he be present. — formal subjunctive
- ✅ Were I to disagree, I would say so. — inverted conditional
These are C1 structures — the CEFR advanced level. At C1 you control inversion, cleft sentences, subjunctive forms, and register-switching fluently across formal and informal contexts.
Marker: if you can restructure a sentence for rhetorical effect without hesitation, you're C1.
Hard
- Had she not intervened, the situation would have escalated. — inverted conditional
- All distractors are grammatically plausible in other contexts
- Multiple rules interact (e.g., tense + aspect + modality)
- Context determines the answer — no single "rule" is enough
Hard marks upper-intermediate to advanced challenges: B2+, interacting rules, edge cases, plausible distractors, and contexts where pattern-matching fails.
Use "Hard" when Easy/Medium feel trivial and you want to test whether you actually understand a rule versus just recognising surface patterns.