Which of the Following Physiological Processes Would Be Considered a Positive

Which of the following physiological processes would be considered a positive feedback mechanism?

A) The release of antidiuretic hormone (ADH) from the posterior pituitary gland
B) Shivering in response to low environmental temperature
C) The platelet aggregation mechanism for closing minute ruptures in very small blood vessels during accidental injury
D) Increased production of white blood cells (WBCs) in response to a microorganism