Choose the appropriate Active Voice of given sentence.

By whom were you taught French?

Who taught you French?

The correct answer is Option (2) - Who taught you French?

In the passive sentence "By whom were you taught French?" the agent (the doer of the action) is introduced by "by whom." When converting to active voice, the agent becomes the subject of the sentence, and "were you taught" is replaced by the simple past "taught." Thus, the sentence becomes "Who taught you French?"