Question

a system in the human body is shown.
the main function of this system is to -
a. excrete hormones throughout the body.
b. send signals back and forth from the brain to the body.
c. circulate blood, nutrients, and gases throughout the body.
d. defend against infections entering the body.

Explanation:

The image shows the nervous - system which has the main function of sending signals between the brain and the body. Hormone excretion is related to the endocrine system, blood - nutrient - gas circulation is the function of the circulatory system, and defense against infections is the job of the immune system.

Answer:

B. send signals back and forth from the brain to the body.