Adult women who spend much time together often begin to have their periods at the same time, because of the influence of chemicals called

A) cytokines.
B) pyrimidines.
C) pheromones.
D) transporters.

Pheromones are chemicals secreted by an organism that can affect the behavior or physiology of other individuals of the same species. In some studies, it has been suggested that pheromones play a role in synchronizing menstrual cycles among women who spend significant amounts of time together. This is known as the "McClintock effect". Cytokines are proteins involved in the immune response, pyrimidines are one of the building blocks of DNA/RNA, and transporters are proteins responsible for moving molecules across cell membranes.