Vanessa Finds Herself Suffering from Extreme Sadness Every Winter

Vanessa finds herself suffering from extreme sadness every winter. She has always been sensitive to the weather, but on some winter days it is very hard for her to get up and get going in the morning. It is dark in the morning when she leaves for school and dark in the early evening when she comes home. Which of the following is most likely responsible for Vanessa's sadness?

A) the lack of sunlight in the morning
B) the body's production of excessive suprachiasmatic nuclei (SCN) during the winter months
C) the circadian rhythm adjusts the body to a 22-hour cycle in the winter months
D) an underactive pineal gland that fails to secrete enough melatonin