Who has broken the mirror? ( Begin : By whom ?)

Which one is correct. a. By whom was the mirror broken ? b. By whom the mirror was broken ? c. By whom has the mirror being broken? d. The mirror has being broken by whom?
( Give explanation for answer )

Dear Student,

The sentence is in active voice. For begining the sentence with 'by whom', we have to convert the sentence to passive voice.

So, correct answer is : By whom has the mirror been broken?
( When you convert interrogative sentences starting with who into passive sentences, we start the sentence with 'by whom'.)
Regards,