The liver removes ammonia from the blood and converts it into urea. Why is this activity of the liver an example of homeostasis?
A. The activity is independent of blood levels of ammonia, and has no effect on the levels.
B. The activity keeps blood levels of ammonia within a certain low range that the body can tolerate.
O C. The activity occurs only during the day, when the body is most active.
D. The activity occurs only at night, when other body organs are at rest.