In contrast to ectotherms, endotherms
a) maintain a lower metabolic rate
b) create and conserve body heat
c) need less to eat
d) are more efficient in warm enviroments

b) create and conserve body heat


Endothermy is a physiological characteristics that enables  some animals to control their body temperature unlike exothermics. This mechanism is important due to sudden change in temperature or uncontrollable conditions set by the harsh environment. 
So birds sharks salamanders and other related animals have this function.

I’m going to go with b!