The Use of Brown Fat to Generate Metabolic Heat Is

Multiple Choice

The use of brown fat to generate metabolic heat is mostly limited to small mammals. Which characteristic of small mammals created the selective pressure that favored the use of brown fat to generate metabolic heat?

A) Small mammals cannot grow enough fur to insulate their bodies.
B) Small mammals have a large surface area to volume ratio, which allows rapid heat loss.
C) Small mammals do not have enough muscle to generate heat by shivering.
D) Small mammals have lost their brown fat through the course of their evolution.