Complete the museum curator's dramatic press release about the missing gemstone. Choose the phrase that correctly uses a double passive construction to show a current belief about a past action.

The cursed diamond _______________ by a notorious syndicate of jewel thieves before the alarm even sounded.

The correct answer is is believed to have been stolen.

This sentence requires a double passive. The first passive (is believed) shows that this is the current consensus of the authorities. The second passive is a perfect passive infinitive (to have been stolen), which indicates that the action happened to the diamond in the past.

The other options incorrectly use active verbs, which would imply the diamond itself has beliefs or was out stealing things!