Question: What action should a receiving entity take upon receipt of a STATUS message indicating an incompatible call control state?
Option 1: Send an ACKNOWLEDGE message to confirm receipt.
Option 2: Clear the call by sending a RELEASE COMPLETE message with cause #101 "message not compatible with protocol state".
Option 3: Ignore the message and continue with the current call setup.
Option 4: Request retransmission of the STATUS message.
Explanation: When a receiving entity receives a STATUS message indicating an incompatible call control state, it should clear the call to prevent any potential issues or conflicts. This is achieved by sending a RELEASE COMPLETE message with cause #101 "message not compatible with protocol state", as specified in the protocol.