Explanation:

- Robbery: This involves taking property from someone by force or threat. Since A used a pistol to threaten Z, this fits the definition of robbery.

- Extortion: This involves coercing someone to give up property due to threat. While A uses a threat, the immediate force and presence of a weapon align more with robbery than extortion.

- Theft: Theft is taking someone's property without consent and without threats or force. A's actions involve threats, so this isn't just theft.

- Dacoity: This involves robbery committed by a group of five or more. Only A and Z were involved here, so it's not dacoity.