Answer: Blood sugar.
Explanation:
The level of sugar in blood is controlled by the help of two hormones insulin and glucagon. There two hormones that controls the level of blood glucose in the body.
When the blood glucose level is more than normal then insulin is released from pancreas to make it normal.
When the Glucose level is less than normal then glucagon helps to elevate the level of blood glucose to make the level normal.
Hence, the correct answer is Option A
