Select the correct Active/Passive form of the given sentence.

The grapes tasted sour.

The grapes were sour when they were tasted.

The correct Active/Passive form of the given sentence is The grapes were sour when they were tasted.

The original sentence is in the Active voice, with the subject "grapes" performing the action of "tasting" sour. However, the verb "taste" is intransitive, which means that it does not take an object. Therefore, the sentence is not grammatically correct in the Active voice.

The passive voice of the sentence would have the grapes as the subject, and the action of "being tasted" would be performed on them. The correct passive voice form of the sentence would be The grapes were sour when they were tasted.

The other options are incorrect. Sour was tasted by the grapes is grammatically incorrect because the verb "tasted" is in the past participle form, but the subject of the sentence is the sourness, which is not an action.

It was sour when the grapes were tasted is grammatically correct, but it is not as concise or natural as the passive voice form of the sentence.

The grapes were tasted sour is grammatically incorrect because the verb "tasted" is in the past participle form, but the adjective "sour" is also used in the sentence. The adjective "sour" should be used to describe the grapes, not the action of tasting them.