Who will write an essay?

By whom will an essay be written?

By whom should an essay be written?

By whom was an essay be written?

By whom can an essay be written?

All of the above

Explanation

Active Voice: Who

Passive Voice: By whom

Who will write an essay means ایک مضمون کون لکھے گا

Future Indefinite Tense

Active Voice Formula: Subject + Will/Shall + Verb (Ist form) + Object + (.)
Passive Voice Formula: Convert Object to Subject + Will/Shall + Be + Verb (3rd form) + By + Convert Subject to Object + Remaining + (.)