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

The tiger killed a deer.

A deer was killed by the tiger.

The correct passive voice of the given sentence is A deer was killed by the tiger.

The active voice of the sentence is The tiger killed a deer. 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 tiger" and the main verb is "kill." The past participle of "kill" is "killed." So, the passive form of the sentence is A deer was killed by the tiger.

The other options are incorrect because:

• A deer had been killed by the tiger. is in the past perfect tense, while the original sentence is in the simple past tense.
• A deer has been killed by the tiger. is in the present perfect tense, while the original sentence is not describing an action that has happened in the past.
• The deer was killed by a tiger. is grammatically correct, but it is not the most concise way to express the passive voice of the sentence.