A particular animal in its natural setting increases its oxygen uptake and metabolic rate in the cold but is unable to maintain its body temperature at a constant level. This animal would be a(n):
A. homeothermic ectotherm.
B. homeothermic endotherm.
C. poikilothermic ectotherm.
D. poikilothermic endotherm.
E. None of the above would apply to this animal.