8. Which of the following is an example of a homeostatic reinforcing feedback loop? Please HIGHLIGHT your selection and explain below.

Andrew was mountain biking and fell and wounded his knee. When tissue is torn or injured, a chemical is released. This chemical causes platelets in the blood to activate. Once these platelets have activated, they release a chemical which signals more platelets to activate, until the wound is clotted.
While exercising, Julia's heart rate and breathing increase to balance the increased oxygen use by her muscle cells.
On a hot day, Martin doesn't drink very much water. His kidneys respond by removing very little water from his blood, resulting in yellow, concentrated urine.
After eating a candy bar, April's pancreas secretes insulin, causing excess blood sugar to be removed.