Question

the culprit confessed his guilt (change the voice )​

Answer 1

Here is the correct answer along with its explanation:

His guilt was confessed by the culprit.

Explanation

The verb in the sentence was Simple Past in the active form (confessed). When we convert the active voice of Simple Past into passive voice, we use passive form equivalent to the active form. The active form in Simple past is 'V2' or Simple Past form of the verb. The object is made the subject and vice versa; 'by' is added. The passive form in Simple Past is was/were +V3.  

Active Voice: S+V2+O.

Passive Voice: O+was/were+V3+by+S.