Question: In the Contact Manager API for Java Card, what is required for a client to receive notifications when a contact is modified in the Contact Manager Server?
Option 1: Implement the `ContactManagerRuntimeEnvironment` interface and use the `register` method.
Option 2: Implement the `ContactEventListener` interface and register for the corresponding events.
Option 3: Directly call the `contactModified` method in the `ContactManagerServer` class when a change is anticipated.
Option 4: Use the `unregister` method to activate notification listening by default.
Explanation: To receive notifications for specific events (like contact modifications), a client must express interest by implementing the `ContactEventListener` interface. This implementation allows the client to define how it will handle the event (e.g., a contact modification). Registering for the corresponding events with the Contact Manager Server is then necessary, so the server knows which clients to notify when such events occur. This approach ensures efficient and targeted event handling in the Contact Manager API ecosystem.