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

The option that is mainly made up of glands and hormones is A. endocrine system. The name itself, coming from a Latin word for gland, suggests that it has a lot of glands which produce hormones in a human body. Nervous system has to do with the brain, whereas the excretory system has to do with the removal of unnecessary materials from the body.