Select the correct passive form of the given sentence.

People say he has lived on liquid diet for years.

He is said to have lived on liquid diet for years.

The correct passive form of the given sentence is He is said to have lived on liquid diet for years.

The sentence "People say he has lived on liquid diet for years" is in the active voice. The active voice is formed by putting the subject of the sentence before the verb and the past participle of the main verb. In this case, the subject of the sentence is "people" and the main verb is "say." The past participle of "say" is "said." So, the active form of the sentence is "People say he has lived on liquid diet for years."

The passive voice 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 "live." The past participle of "live" is "lived." So, the passive form of the sentence is He is said to have lived on liquid diet for years.

The other options are incorrect because:

• He has said to have lived on liquid diet for years is grammatically incorrect. The verb "to say" is followed by a direct object, but the phrase "he has said to have lived on liquid diet for years" does not have a direct object.
• He is said to have been living on liquid diet for years is in the present perfect tense, while the original sentence is in the simple past tense.
• He is said to live on liquid diet for years is in the present tense, while the original sentence is in the simple past tense.