Rewrite the sentence in active voice.
By whom was this work done?

Correct option is B

Explanation: The passive question "By whom was this work done?" should be converted to an active voice question "Who did this work?" This reflects a simple past inquiry about who completed the work, maintaining the directness and simplicity of the original query.
Past indefinite
Subject + V2 + object. -> <- Object + auxiliary verb (was, were) + past participle + by + subject.
Example: By whom were the cookies eaten? -> Who ate the cookies?