What type of system is required to maintain the amount of sugar in the blood at a certain level, making sure it does not rise too high or fall too low?

The Digestive system.

Explanation:

Even though the Cardiovascular system pumps the blood in the body, blood sugar is dependent on the regulating hormones insulin and ketone. Which are created in the liver. And the liver is part of the Digestive system. Diabetes, hypoglycemia and hyperglycemia are results of a faulty liver.

well we can't tell you because we cant see the time give a screen shot or something.

sorry to break it to ya but no one can answer your question it's just

jk but i am serious about the part that most people cant answer it beacuse you did not mention the section you are talking about. but it would if you added some detail and were a bit more specific.