Select the option that expresses the given sentence in passive voice.

In the theatre, the audience threw flowers on the screen.

In the theatre, flowers were thrown by the audience.

The correct passive voice of the given sentence is In the theatre, flowers were thrown by the audience.

The active voice of the sentence is In the theatre, the audience threw flowers on the screen. This sentence is in the simple past tense, which is used to describe an action that happened in the past. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "the audience" and the main verb is "throw." The past participle of "throw" is "thrown." So, the passive form of the sentence is In the theatre, flowers were thrown by the audience.

The other options are incorrect because:

• In the theatre, flowers had been thrown by the audience. is in the past perfect tense, while the original sentence is in the simple past tense.
• In the theatre, flowers was thrown by the audience. is grammatically incorrect. The verb "was" is singular. The subject of the sentence is "flowers," which is plural.
• In the theatre, flowers are thrown by the audience. is in the present tense, while the original sentence is in the simple past tense.