Which of the following serves as an effector, or part of an effector, that functions in a negative feedback system?
A. 1,25-dihydroxyvitamin D Receptors located intracellularly in cells in the intestine.
B. Oxytocin Receptors (OXRs) located in the plasma membranes of cells in the walls of the uterus of a pregnant female.
C. CaSRs (Calcium-Sensing Receptors) in the plasma membranes of cells in the Parathryroid Gland.