Select the most appropriate option to fill in the blank.

It was ______ who encouraged me while I was sunk in despair.

he

The correct option to fill in the blank is he.

The pronoun "he" is in the nominative case, which is used as the subject of a sentence or a clause. In the sentence "It was he who encouraged me while I was sunk in despair," the pronoun "he" is the subject of the clause "who encouraged me."

The other options are not in the nominative case. The pronoun "our" is in the possessive case, the pronoun "us" is in the objective case, and the pronoun "we" can be in either the nominative or the objective case.