Which of the following sentence is in the passive voice?

The cat was chasing the mouse.

The cat has chased the mouse.

The mouse is chased by the cat.

The cat chases the mouse.

The mouse is chased by the cat.

This sentence is in the passive voice because the subject (the mouse) is receiving the action, and the doer (the cat) comes after "by."

Passive voice focuses on the action being done to the subject.