A fox is a type of mammal that is related to dogs. How does a fox most likely respond to hot air temperatures in a way that ectothermic animals cannot?

By panting or breathing heavily.

Explanation:

An ectothermic animal is one whose body temperature depends on the temperature of the external environment.

The body of ectotherms regulates temperature depending on the temperature of the external environment where such animal finds itself.

Hence, when the temperature of the external environment rises as a result of hot air, the body of an ectotherm (that is homeothermic, that is, maintain a relatively constant body temperature irrespective of the temperature of the external environment) will adjust so as to keep its temperature relatively constant.

Dogs generally pant (breathe heavily) to bring their body temperature back to normal whenever it rises beyond normal due to rigorous physical activities or high external temperature.

Hence, a fox will most likely pant in response to hot air temperature just like dogs.

"a.) well–developed vascular system."