Nathan's Roommate Just Startled Him by Jumping Out from Behind

Multiple Choice

Nathan's roommate just startled him by jumping out from behind a chair and yelling 'boo'.As soon as Nathan realized that this was just a gag,what part of his nervous system would help him calm down?

A) the sympathetic nervous system
B) the parasympathetic nervous system
C) somatic nervous system
D) central nervous system