Many stories were written by Mike.
Active Voice: Mike has written many stories.
Passive Voice: Many stories have been written by Mike.
(1)ответ: have been
(2)ответ: written
Many stories were written by Mike.
Active Voice: Mike has written many stories.
Passive Voice: Many stories have been written by Mike.
(1)ответ: have been
(2)ответ: written