Describe the maintenance signs indicating insulator replacement is necessary.

The indication that replacement of an insulator is necessary is best represented by signs such as cracks, discoloration, or changes in electrical resistance readings. When insulators experience physical damage—like cracks—they can lose their ability to effectively withstand electrical currents, leading to a significant risk of electrical failures or safety hazards. Discoloration often signals material degradation, which can be caused by environmental factors or prolonged exposure to electrical stress. Similarly, changes in electrical resistance readings can indicate that the insulator is no longer functioning within its required specifications, potentially compromising system performance and safety. Recognizing these signs early allows for proactive maintenance, avoiding system failures and ensuring the integrity of electrical installations.

In contrast, waiting for a complete system failure, only considering color and weight loss, or relying solely on the feel of the insulation can lead to significant risks and inefficiencies, making option C the most comprehensive and safety-oriented choice for insulator maintenance.