Studies Involving Transections at Different Levels of an Animal's Nervous

Studies involving transections at different levels of an animal's nervous system have suggested that REM sleep occurs

A) only if the cut is caudal to the pons.
B) only in animals with brains that have not been transected.
C) only if the cut is rostral to the pons.
D) in whichever part of the transected brain contains the pons.