Question

what did you discover?
who knocked on the door?
change into passive voice

Answer 1

What was discovered by you?

By whom was the door knocked?

..

Answer 2

$\huge{\mathfrak{Question}}$

What did you discover ?

Who knocked on the door?

$\huge{\mathfrak{Answer}}$

What was discovered by you?

By whom was the door knocked?

Active voice

A verb is in the Active voice when its form shows that the person or thing denoted by the subject does something; or is the doer of the active.

Example

Ram helps Sita.

Passive voice

A verb is in passive voice when its form shows that something is done to the person or thing denoted by the subject.

Example

Sita is helped by Ram.