Which of the following serves as a sensor, or as part of a sensor, that functions in a positive feedback system?
A. CaSRs (Calcium-Sensing Receptors) situated in the plasma membranes of Parathyroid Gland cells.
B. Parathryroid Hormone Receptors (PTHRs) located in bone cells.
C. Oxytocin Receptors located in cells in the walls of the uterus of a pregnant female.