Which of the following sentences is in the Passive Voice?

In English grammar, voice shows whether the subject of a sentence performs the action (active voice) or receives the action (passive voice). A canonical passive sentence is built with a form of 'to be' plus the past participle of the main verb (e.g. 'the letter was written'), where the doer of the action, if mentioned at all, is introduced with 'by'. A causative passive is a related passive pattern: 'subject + was/were + made + to + base verb' (e.g. 'was made to surrender'), where the subject undergoes an action that someone else compels, rather than acting purely on their own initiative.

In the sentence 'He was made to surrender his passport', the main verb 'was made' is a passive form (be + past participle) built from the causative verb 'make' — some other, unnamed person compelled 'He' to act. 'He' does carry out the embedded action of surrendering (handing over) the passport, but only because he was made to; it is this passive main verb 'was made' that marks the sentence's overall structure as Passive Voice.

Checking the other sentences confirms none of them is passive:

• 'They feed the lions in the zoo twice.' — the subject 'They' directly performs the action 'feed' on the object 'the lions'; this is Active Voice.

• 'A jelly-fish stung her' — the subject 'A jelly-fish' performs the action 'stung' on the object 'her'; this is Active Voice.

• 'We will not admit children under sixteen.' — the subject 'We' performs the action 'admit' on the object 'children under sixteen'; this is Active Voice.

Therefore, the sentence 'He was made to surrender his passport' is the only one in the Passive Voice.