In Fast-Swimming Cool-Water Fishes Such as Sharks and Tunas, Which

In fast-swimming cool-water fishes such as sharks and tunas, which of the following contribute(s) to the generation and maintenance of core body temperatures in excess of ambient water temperatures?

A) Specializations in the size and arrangement of blood vessels
B) Low rates of activity in the swimming muscles
C) An ability to acclimatize rapidly to the surrounding water
D) Metabolic rates that are insensitive to temperature change
E) An insulating layer of fat located beneath the scaled skin.