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’.
I am watching a movie, when my mother came into the room.

Correct option is B

The correct substitution is (b) I was watching.
Explanation:
· The use of "came" indicates past tense, so the clause before it must also be in past continuous.
· “I am watching” (present continuous) is tense mismatch.
Grammatical Rule Used:
· When two actions happen in the past, and one is in progress when another occurred, use past continuous + simple past.
Example:
· I was reading when she called me.
Information Booster:
· “When” clauses often trigger the use of past continuous in the main action.