An increase in blood solute concentration, as measured by the osmoreceptors of the hypothalamus, indicates a net loss of water in the body. The hypothalamus responds by both stimulating a thirst response and releasing antidiuretic hormone. Antidiuretic hormone directs the kidneys to recover more water during urine production. In this case, what two parts of a feedback loop are occurring in the hypothalamus?

• A. The control center and the response.
• B. The receptor and the control center.
• C. The control center and the effector.
• D. The receptor and the effector.