Exercises
1Correct the modal error: "She must to apologise for her behaviour."
Modal verbs are followed directly by the base form — never by "to".
2Rewrite as a certain deduction about the past: "I'm sure she left already."
Epistemic "must have + PP" expresses a confident deduction about a past event.
3Rewrite using a modal adverb instead of a modal verb: "It is certain that the plan will succeed."
Modal adverbs (undoubtedly, certainly, clearly) express the same stance more fluently in formal writing.
4Rewrite as a hedged, tentative academic claim: "Automation causes unemployment."
Tentative modal phrasing ("may be argued", "appears to") softens a claim for academic register.
5Rewrite expressing an unused past ability: "I had the ability to help, but I chose not to."
"Could have + PP" expresses an unrealised past possibility or ability.
6Rewrite as a confident negative deduction about the past: "I'm sure he didn't see the message."
"Can't have + PP" is the negative counterpart of "must have + PP" for confident past deductions.