Choose the most suitable option to replace the highlighted part of the sentence: You must prevent your brother to do such things.

Correct — A. The trigger is prevent, which takes the pattern prevent + person + from + -ing: prevent someone from doing something.

It does not take a to-infinitive, so 'prevent your brother to do' is the error.

With from + -ing the sentence reads: 'You must prevent your brother from doing such things.' → option (a).

Why the others are wrong

• (b)
  of doing such things — Of is the wrong preposition. Prevent pairs with from; of doing belongs to other verbs, as in accuse someone of doing something.
• (c)
  not to do such things — Not to do keeps the to-infinitive that caused the error. The not also doubles the negative that prevent already carries.
• (d)
  doing such things — Prevent + person + -ing, without from, is labelled British English in Oxford Learner's Dictionaries. From doing is the pattern it lists with no label, so option (a) is the more suitable replacement.

Prevent, prohibit, deter, discourage and dissuade all take from + -ing: dissuade someone from doing something.

The to-infinitive belongs to a different group — want, ask, tell, advise: ask him to go. Prevent is not in that group.

After a preposition such as from, English uses the -ing form: from doing, never from do.

Key facts

• Prevent takes prevent + person + from + -ing: prevent him from leaving.
• Prohibit, deter, discourage and dissuade take the same from + -ing pattern.
• After a preposition such as from, a verb takes the -ing form.

Common traps

• Using a to-infinitive after prevent by analogy with ask or tell — prevent takes from + -ing.
• Choosing not to do because prevent sounds negative — prevent already carries the negative.

No directly related past PYQ was found.