Which of the following characteristics relates to a cavy's health?

The characteristic that relates to a cavy's health is the good condition of the coat. A healthy cavy typically has a clean, well-groomed coat that is free from mats, excessive oil, or any signs of skin irritation. The coat condition can indicate proper nutrition, grooming practices, and overall well-being. For example, a dull or scruffy coat may suggest nutritional deficiencies, health issues, or inadequate care, while a shiny and neat coat reflects good health and care.

Good ears and correct ear numbers can relate more to the cavy's conformation and standards in showmanship rather than health, while correct color primarily pertains to breed standards rather than an indication of health status.