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?

A. one negative and one positive feedback loop
B. two positive feedback loops
C. one negative feedback loop
D. two negative feedback loops

Explanation:    Toghether, insulin and glucagon help maintain a state called homeostasis in which conditions inside the body remain steady. When blood sugar is too high, the pancreas secretes more insulin. When blood sugar levels drop, the pancreas releases glucagon to raise them.

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation: