When a person rises quickly from a prone position,
a.the cardioaccelerator center in the medulla becomes less excited?

When a person rises quickly from a prone position, Reflex vasoconstriction of peripheral blood vessels occurs.
Reflex vasoconstriction happens when blood vessels became temporarily narrowed due to a sudden contraction of the muscular wall of the vessels which could temporarily restrict your body's movement

22·20 you would use the sum it up method