Why Would Most of the Females in a College Dormitory

Why would most of the females in a college dormitory tend to have their menstrual cycles synchronized after living together for an extended period of time?

A) The sight of blood tends to induce menstruation in females.
B) Since females tend to be very social,communicating about bodily physiology induces changes in other females' physiology.
C) Pheromones released during the menstrual cycle bind to a receptor in other females that alters their normal menstrual cycle.
D) Steroidal hormones released from the gonads can induce physiological changes in other females if direct physical contact occurs.