Question

this hormone causes the liver to release glucose into the blood to raise blood glucose levels. insulin glucagon serotonin aldosterone

Explanation:

Insulin lowers blood - glucose levels. Glucagon stimulates the liver to release glucose, raising blood - glucose levels. Serotonin is a neurotransmitter not directly related to this function. Aldosterone is involved in salt and water balance, not blood - glucose regulation.

Answer:

Glucagon