What is the most obvious form of chafing?

The most obvious form of chafing is exterior damage to a cable. This type of damage occurs when a cable comes into contact with a sharp edge or abrasive surface, leading to wear and potential exposure of the internal conductors. As cables are frequently subject to movement and vibration during operation, any signs of fraying, cuts, or visible wear on the outer insulation are strong indicators of chafing. Identifying this issue is critical, as it can result in electrical shorts or failures if left unaddressed, potentially compromising the functionality and safety of the aircraft's systems.

The other options, while they may relate to electrical problems, do not specifically highlight the characteristic and direct manifestation of chafing. Burnt circuit boards, faulty fuses, and loose connections can arise from a variety of issues but are not as visually obvious as the damaged exterior of a chafed cable.