Explanation:

- No offence: This does not apply as X has clearly committed an unlawful act by instilling fear.

- Criminal misappropriation: This involves dishonestly misusing someone's property already in your possession, not inducing someone to sign a document.

- Extortion: This occurs when someone unlawfully obtains something from another through coercion or threats. Here, X instills fear of grievous hurt to make Z sign the paper.

- Robbery: This involves theft with violence or threat, but here there's no immediate transfer of property through force.

Correct Answer: Extortion