Question

Choose the word or phrase that best completes the sentence.

He couldn't rest or sleep because __________ too much coffee.

• A. Drinking
• B. Been drinking
• C. Had been drinking
• D. He had been drinking

Answer 1

The correct option is D He had been drinking

Here, 'He had been drinking' in past perfect continuous is correct because it is used to indicate an action in the past that began before a certain point in the past and continued up until that time.
'Had been drinking' is incorrect because of the missing subject (he).
Usage of 'drinking' and 'been drinking' is grammatically incorrect.