Answer :
Explanation :

Passive Voice : Has the work been completed by him?   Rules in changing from Active voice to Passive voice : 1. Identify the subject, the verb and the object: S+V+O 2. Change the object into subject 3. Put the suitable helping verb or auxiliary verb 4. Change the verb into past participle of the verb 5. Add the preposition "by" 6. Change the subject into object.