The correct option is A Has the opposite effect as that of insulin
Pancreas is a large organ present in abdomen and serves as both endocrine and exocrine organ. The endocrine parts of pancreas are islets of Langerhans that have two primary cell types namely, alpha and beta cells. Alpha cells of islets produce and secrete glucagon hormone while beta cells produce insulin. This makes option B incorrect. Insulin serves to lower the blood glucose level by stimulating the uptake of glucose by cells, specifically muscle cells, liver cells and adipose tissues cells. Glucagon hormone from pancreas stimulates liver to break down glycogen into glucose and use of fat and protein as glucose source thereby increasing the blood glucose level. This makes option C incorrect. Option A correct as both hormones regulate the blood sugar level by their antagonistic effects. Option D is incorrect as diabetes mellitus is caused by under secretion of insulin; not that of glucagon.