The Passive form of '"Who did this ?"
A"By whom is this done ?"
B"By whom was this done ?"
C"By whom is this being done ?"
D"By whom has this done ?"
A"By whom is this done ?"
B"By whom was this done ?"
C"By whom is this being done ?"
D"By whom has this done ?"
Related Questions:
The Passive form of "Will the police arrest the union leader ?"
The Passive voice of " Is she eating a cake ?"