Lulu Is 53 and Has Not Had Her Menstrual Period

Lulu is 53 and has not had her menstrual period in a year. Several times a day, she feels a tingling in her upper chest, and then heat washes over her, in an upward direction. It is intensely uncomfortable for about 5 minutes, during which she is nearly overwhelmed with an urge to fling off her clothing. The cause of Lulu's hot flashes is

A) an increase in gonadotropin concentration and a decrease in estrogen concentration.
B) an increase in gonadotropin concentration and an increase in estrogen concentration.
C) a decrease in gonadotropin concentration and an increase in estrogen concentration.
D) a decrease in gonadotropin concentration and a decrease in estrogen concentration.