C. Alligators basking in the sun on a rock matches the homeostasis strategy of kleptothermy.

Kleptothermy is a strategy used by some organisms to maintain their body temperature by stealing or borrowing heat from an external source, rather than generating their own heat. Alligators are cold-blooded animals, which means their body temperature is regulated by the environment. By basking in the sun on a rock, the alligator allows its body to absorb heat from the sun to increase its body temperature. The alligator can then use this heat to carry out metabolic processes and maintain its body temperature.

Penguins having dark coloring to absorb more radiation from the sun is called thermoregulation by pigmentation.
A dog panting at the park on a hot summer day is a way of thermoregulation by evaporation.
People huddling together on New Year's Eve in Times Square is an example of thermoregulation by social behavior.