Identify a factor that can contribute to increased risk of termite infestation in homes.

Wood-to-soil contact significantly increases the risk of termite infestation in homes. Termites primarily feed on cellulose, which is abundant in wood. When wooden structures, such as decks, fence posts, or home foundations, are in direct contact with the soil, they provide an accessible food source for termites. This contact can also create a more favorable environment for termite activity, as moisture and warmth often accumulate around the wood in contact with the ground.

In contrast, high humidity levels may create a humid environment that is conducive to termite survival and activity, but it does not directly provide the food source that wood-to-soil contact does. Frequent cleaning generally doesn't contribute to termite issues and instead can help in detecting potential signs of termite activity. Lastly, while metal siding may prevent termites from accessing the wood underneath, it does not eliminate the risk if other wood components, such as a home’s frame or structural supports, are in contact with the soil.