Which of the following is an example of negative feedback in the endocrine system?

a. when the amount of a hormone reaches a certain level, the endocrine system stops releasing that hormone.
b. when a hormone travels through the bloodstream, it will interact only with its target cells.
c. after age 40 or so, people’s muscle strength begins to decrease and their skin starts to wrinkle.
d. when people are startled by a frightening event, their hearts beat faster and their breathing increases.