Michael Has Gained 10 Pounds Since He Became Close Friends

Michael has gained 10 pounds since he became close friends with Matt,who is 75 pounds overweight.Michael finds that he eats larger portions and more unhealthy foods when he is around Matt.Michael's change in diet and weight gain can be explained by the impact of

A) the basal metabolic rate.
B) narcissism.
C) sleep loss.
D) social influence.