Which of the following is a sign of dental disease in pets?

Bad breath, or halitosis, is a significant indicator of dental disease in pets. This occurs due to the buildup of plaque and tartar on the teeth, which can lead to gum inflammation and infection. As bacteria multiply in the mouth, they produce foul-smelling compounds that contribute to the noticeable odor. Therefore, when a pet exhibits bad breath, it often suggests underlying dental health issues that may require veterinary attention, such as periodontal disease or tooth decay.

In contrast, the other options do not specifically relate to dental disease. A soft, shiny coat typically signifies good nutrition and health, increased energy is often an indication of general well-being or may suggest effective management of a condition, and regular eating habits do not necessarily point to issues with dental health. For these reasons, while they might reflect aspects of overall pet health, they don't correlate directly with dental disease like bad breath does.