Select the most appropriate option that can substitute the highlighted words in the given sentence.
I had been waiting an hour when you came to see me.

Correct option is D

The correct substitution of the highlighted words is (d) no improvement.
Explanation: The sentence correctly uses the Past Perfect Continuous Tense, which is used to show that an action was ongoing for a duration of time in the past before another event took place.
Grammatical rule used:
�� Past Perfect Continuous Tense: had + been + present participle (V1+ing)
Example: She had been reading for two hours when I called.
�� Information Booster: This tense highlights the duration of an activity that was happening before another past event.