I forgot ______ the door, so someone could get in.
Answer and explanation
Correct answer: A. to lock
- Step 1: 'Forget to do' means failing to do a necessary action.
Answer
to lock.
Why not the others: locking, lock and to have locked don't fit.
Practise more Non-finite verbs and passive.
Free questions with an explanation for every one, and full timed College English Test Band 4 (CET-4) - China mock tests.