Which of the following indicates that brake shoes need to be replaced?

Answer: B — Excessive wear and noise during operation

Brake shoes are a critical component of a vehicle's air brake system, and their condition directly affects braking performance. When brake shoes begin to wear down excessively, they can produce noticeable signs such as increased noise during operation and reduced braking efficiency. If you hear a grinding or squeaking sound while braking, it usually indicates that the friction material on the brake shoe has worn to a point where it's no longer effective. This excessive wear can compromise safety by leading to longer stopping distances or even brake failure. Monitoring for noise and signs of wear is essential for maintaining a vehicle's braking system. Regular inspections can help identify these issues before they escalate. Each of the other options, such as improved braking efficiency, increased air pressure, and new brake fluid, do not serve as indicators for replacing brake shoes; rather, they refer to conditions or maintenance aspects unrelated to brake shoe wear.