Rewrite the sentence in active voice.
Our house was built by my father.

Correct option is D

Explanation: The passive voice sentence "Our house was built by my father" directly converts into the simple past active voice, "My father built our house." This reflects a completed action in the past without any indication of the action's continuation or a specific time frame, which is best expressed in simple past tense.
Conversion Rule: Past indefinite
Subject + V2 + object. -> <- Object + auxiliary verb (was, were) + past participle + by + subject.
Example: The cake was made by her. -> She made the cake.