When is it appropriate to use the passive voice?

Question

1. When the person or thing performing the action is a proper noun
2. It is never appropriate to use the passive voice
3. When the person or thing performing the action is unimportant or unknown
4. When the person or thing performing the action comes before the verb

Answer 1

3. When the person or thing performing the action is unimportant or unknown

This is the most common use of the passive voice.