Torpor Has Evolved in Several High-Latitude Species Even Though It

Torpor has evolved in several high-latitude species even though it is energetically expensive.Why does this adaptation require a large energy input for those species that utilize this function?

A) These animals expend a great deal of metabolic energy to maintain their body temperature as the ambient temperatures drop.
B) It takes a great deal of energy to stay alive when the body temperature drops to near ambient levels.
C) During torpor,animals undergo excessive shivering to maintain their body temperature.
D) Animals in torpor lower their body temperature dramatically and require a great deal of energy to bring the body temperature back up to normal.