Final answer:
The bleed leak-detection system monitors pneumatic ducting downstream of the engine bleed valve, ensuring the integrity and safety of the aircraft's high-pressure air systems.
Step-by-step explanation:
The bleed leak-detection system in an aircraft is designed to monitor the integrity of the pneumatic ducting. Specifically, this system is usually concerned with detecting leaks downstream of the engine bleed valve. The correct option here is c) Engine bleed valve. The pneumatic ducting system is critical for various aircraft operations, as it provides high-pressure air for systems including environmental control, ice protection, and pressurization. Detecting leaks promptly ensures the safety and proper functioning of these systems.