Step 1: Definition of extortion under IPC Section 383.
- Extortion occurs when a person intentionally puts another in fear of injury and thereby dishonestly induces them to deliver property or valuable security.
- “Injury” under IPC includes harm to body, mind, reputation, or property.
Step 2: Application to the given facts.
- Here, A threatens to harm Z’s reputation by publishing defamatory material.
- This creates fear of injury to reputation, fulfilling the element of “putting in fear of injury”.
- The threat is used to dishonestly induce Z to give money — fulfilling the element of delivery of property due to fear.
Thus, this is a textbook case of extortion under IPC.
\[
\boxed{(a)}
\]