Unlike Humans, Kangaroos Can Increase Their Movement Speed Without an Increase

Unlike humans, kangaroos can increase their movement speed without an increase in their metabolic rate because

A) their diet is more energy-rich than ours is.
B) they have more mitochondria per cell than we do.
C) the recoil in their elastic tendons helps power each jump.
D) they convert starch directly to ATP without first hydrolyzing it to glucose.
E) they alternate which foot they use each time they jump.