What term describes animals that generate a small amount of metabolic heat but also rely on external heat sources to regulate their body temperature?

Explanation

Endotherms (Option A) generate most of their heat metabolically to maintain a stable temperature. Ectotherms (Option B) rely solely on environmental heat. Homeotherms (Option D) maintain constant body temperature. Heterotherms (Option C) produce some metabolic heat but also absorb heat from their surroundings, combining both strategies.