Question:
The protein which controls the amount of sugar in the blood is:
A.Hemoglobin
B.Oxytocin
C.Insulin
D.Ptyalin

Hint: Insulin is responsible for controlling blood sugar level which is produced in the pancreas.

Complete step by step answer:
Hemoglobin A - Hemoglobin A is a protein present in red blood cells and helps in carrying oxygen to our body tissues and organs and also transport \[C{O_2}\] from tissues and organs back to our lungs. Thus, it does not control the sugar in the blood.
Oxytocin - Oxytocin is a hormone which acts on different organs of our body and also works as a chemical messenger for the brain and controls the reproductive system. Thus, it also does not control the sugar in the blood.
Insulin- Insulin is a hormone and is produced in the pancreas which is situated near the stomach. It helps one's body to use glucose and then produce energy. And now to define Glucose, it is a type of sugar that is found in many carbohydrates. After meals, insulin then absorbs sugar from glucose absorbed in our bloodstream and provides energy. This way it also balances blood glucose level.
Ptyalin - It is not a type of hormone but a form of amylase that is found in the saliva of human beings and animals. Thus, it also does not control the sugar in the blood.
So, the protein which controls the amount of sugar in the blood is Insulin.

Therefore, the correct answer is option (C)

Note: Insulin is a natural hormone produced by pancreas in our body and controls the use of glucose in our body. When protein is ingested in the body then the insulin is released plus it is also released when the glucose is present in the body.