Select the correct passive form of the given sentence.

The gardener has watered the bushes.

The bushes have been watered by the gardener. 

The correct passive form of the given sentence is The bushes have been watered by the gardener.

The active voice of the sentence is The gardener has watered the bushes. This sentence is in the present perfect tense, which is used to describe an action that has happened in the past but is still relevant to the present. 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 "bushes" and the main verb is "water." The past participle of "water" is "watered." So, the passive form of the sentence is The bushes have been watered by the gardener.

The other options are incorrect because:

• The bushes are being watered by the gardener. is in the present continuous tense, which is used to describe an action that is happening now but is not finished. The sentence is describing an action that has already happened, so the present continuous tense is not appropriate.
• The bushes were being watered by the gardener. is in the past progressive tense, which is used to describe an action that was happening in the past but is not finished. The sentence is describing an action that has already happened, so the past progressive tense is not appropriate.
• The bushes has been watered by the gardener. is grammatically incorrect. The verb "to water" needs to be in the past participle form, which is "watered."
• The bushes has been watered. is missing the agent, which is the person or thing that did the action. The passive voice of a sentence should always include the agent.