Which of the following is an example of a negative feedback loop?
a) Arctic glaciers and sea ice melt due to warming, and darker surfaces are exposed, which absorb more sunlight, which causes more warming and further melting.
b) The brain responds to heat by telling the body to cool down by seeking shade or sweating, thus the body cools. If the body is too cold, the brain tells the body to seek more clothing or begins to shiver, and the body warms.
c) An apple on the tree ripens, which produces ethylene, which signals the apple's neighbors to ripen, which makes the neighbors produce ethylene, which causes more apples to ripen.
d) Wounded tissue releases chemicals to signal platelet activation, which then signals the release of more chemicals, where the wound clots.