Read the paragraph.

(1) Last week, our English class watched a hilarious movie based on a novel. (2) In it, a couple of incompetent thieves bungle their way through a heist. (3) After several escapades, a priceless painting is stolen by the thieves. (4) But then, the thieves make an impressive blunder and accidentally return it.

Which sentence in the paragraph is in the passive voice?

Sentence 1
Sentence 2
Sentence 3
Sentence 4