Compared to "Cold" Fish, "Hot" Fish, Such as Bluefin Tuna

Compared to "cold" fish, "hot" fish, such as bluefin tuna, keep a higher temperature difference between their body and the surrounding water because they

A) produce thermogenins.
B) have a countercurrent heat exchange system of veins and arteries.
C) shiver to create more heat.
D) have many brown fat tissues.
E) have a large dorsal aorta that keeps them warm.