Select the correct passive form of the given sentence.

A stranger buys flowers for the dead man's grave.

Flowers are bought by a stranger for the dead man's grave.

The correct passive form of the given sentence A stranger buys flowers for the dead man's grave is Flowers are bought by a stranger for the dead man's grave.

The active voice of the sentence is A stranger buys flowers for the dead man's grave. This sentence is in the simple present tense, which is used to describe an action that happens regularly or habitually. 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 "flowers" and the main verb is "buy." The past participle of "buy" is "bought." So, the passive form of the sentence is Flowers are bought by a stranger for the dead man's grave.

The other options are incorrect because:

• Flowers is bought by a stranger for the dead man's grave. The subject of the sentence is "flowers," so the verb "is" should be "are."
• Flowers were bought by a stranger for the dead man's grave. This sentence is in the past tense, but the action of the flowers being bought happens regularly or habitually. The simple present tense is more appropriate in this case.
• Flowers have been bought by a stranger for the dead man's grave. This sentence is in the present perfect tense, which is used to describe an action that happened in the past and is still relevant to the present. There is no indication that the flowers have been bought recently, so the present perfect tense is not appropriate.