Select the most appropriate option that can substitute the highlighted segment in the given sentence. If there is no need to substitute it, select ‘No substitution required’.
While the online class was going on, they had to keep their cameras on.

Correct option is C

The correct substitution of the highlighted words is (c) No substitution required.
�� Explanation:
· The sentence is in the past continuous and past obligation form.
· “While the class was going on” → indicates past duration.
· “They had to keep” → correct form for expressing a past necessity.
· The verb “ keep” is in base form, correctly following the modal “had to.”
Example:
· During the meeting, they had to turn off their microphones. ✅
✅ Grammatical Rule Used:
✔ “ Had to + V1” = expresses past compulsion or necessity.
✔ Verb form following “had to” must be in base form (keep, not keeping or kept).
�� Grammar Booster:
�� Have to (present), Had to (past), Will have to (future) + base verb → express obligation