Which one of the following human organ systems is mainly made up of glands and hormones? a. endocrine system b. excretory system c. nervous system

Endocrine system is the human organ system that is made up of glands and hormones.

Option A

Explanation:

The "endocrine system" is responsible for secretion of hormones inside the body and it is made up of endocrine glands such as thyroid glands, pituitary glands, pineal gland, adrenal gland, pancreas, ovaries and testes. These glands releases hormones into the blood to target organs which are situated at a distance or into nearby tissue to target nearby cells or to target self. Endocrine glands works by forming negative and positive feedback loops to regulate the proper functioning and effect of the hormone on the target organ or cells and for control the production of hormone from the glands itself.

the dark variety, as they are not visible on the dark tree barks

explanation:

i think the answer is b.