Which of the following is a sign of a termite infestation?

The presence of mud tubes and wood damage is a clear indicator of a termite infestation. Termites typically construct mud tubes to protect themselves from predators and to maintain moisture while traveling between their nest and food sources, which often include wood. These tubes can often be found along the foundation or walls of a home. Additionally, termites cause noticeable damage to wooden structures, which may manifest as hollowed-out wood, frass (termite droppings), or polished areas on the wood’s surface.

In contrast, the other options provided do not directly indicate a termite problem. Dust accumulation can occur for various reasons, such as lack of cleaning and does not specifically point to termites. An increased presence of houseflies may suggest issues with sanitation or decomposition but is unrelated to termite activity. Unattended food sources typically relate to other pests, such as rodents or ants, rather than termites, which primarily feed on wood. Thus, the specific signs associated with mud tubes and wood damage make it the definitive choice for identifying a termite infestation.