Which of the following best explains why this is an example of a negative feedback loop? (please read each choice carefully)

a. when the levels drop below their set point, the pancreas brings it back to the set point

b. it is the process that puts sugar into our blood

c. it adds more and more sugar to our blood so that we can make ATP

d. when sugar levels drop below or rise above the set point, we have mechanisms in place to bring the sugar levels back to a set point.