Choose the most suitable option to replace the highlighted part of the sentence:
It is high time you must change your habits.

Correct option is A

The correct substitution of the highlighted words is (a) changed your habits. Explanation: The expression “It is high time” is followed by a subject + past simple to show that something should already have happened.
Using must after “high time” is incorrect because the structure itself already carries the sense of urgency/necessity. Hence, “It is high time you changed your habits” is grammatically correct.
Grammatical rule used:
· It’s high time + subject + past simple (to express urgency/overdue action)
· Example: It is high time we started taking health seriously.
· Information booster / exceptions related to grammatical topic:
· “High time” = “अब देर हो चुकी है”—but grammar uses past tense, not because it is past time, but because it shows overdue/expected action.