Question

He Had (Think) Of A Good Answer To The Question

Answer 1

Answer:

He had thought of a good answer to the question.

OR

He had been thinking of a good answer to the question.

Explanation:

Here, HAD is past tense ,hence in addition to it, past tense of THINK i.e. THOUGHT will be used in the blank to complete the sentence.

Second thing could be...

He had been thinking of a good answer to the question.

This is because on adding been + ing form of the verb, the sentence will turn into past perfect continuous tense which too will be correct.

Answer 2

Answer:

He had thought of a good answer to the question.

Explanation:

it is the form of past perfect tense.