The correct passive voice form of the given sentence is He was not fed by anybody when he was starving.

The active voice of the sentence is "Nobody fed him when he was starving." 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 "he" and the main verb is "feed." The past participle of "feed" is "fed." So, the passive form of the sentence is "He was not fed by anybody when he was starving."

The other options are incorrect because:

• He had not been fed by anybody when he was starving. This sentence is in the past perfect tense, which is used to describe an action that happened in the past before another action happened. However, in this case, the action of not being fed is not relevant to the present.
• He is not fed by anybody when he is starving. This sentence is in the present tense, but the action of not being fed happened in the past.
• He were fed by nobody when he was starving. The word "were" is not used in the passive voice in the simple past tense. The correct form is "was."
• He were fed by nobody when he was starving. This sentence is grammatically incorrect. The subject of the sentence is "he," which is singular. Therefore, the verb "were" should be "was."