Answer:
Option-D
Explanation:
Endocrine system refers to the body organs called glands which produce hormones which can control the important functions of the body. The endocrine system is controlled and regulated by the other hormonal level, the neurons and the changes in the blood level.
Among these three, the least complicated system which controls the endocrine gland in the humoral stimulus which can control the endocrine system by measuring the concentration of the blood ions and the nutrients. The case of the production of insulin by the pancreas is directly controlled by the concentration of glucose in the blood.
Thus, Option-D is the correct answer.
