The primary purpose of the endocrine system is
a. body repair
b. maintenance of homeostatsis
c. coordination of movement.
d. response to external stimuli
e. information storage

D. Response to external stimuli  

Explanation:

The endocrine system is responsible for the production of hormones that regulate the most diverse physiological activities of the organism. It works together with the nervous system, in perfect sync that works as follows: nervous system receptors pick up external stimuli and from them induce the endocrine system to react.

For this reason, we can conclude that the main purpose of the endocrine system is to respond to external stimuli.

answer; ///(b) it is composed of four protein chains and four heme groups;

above statement is not a true statement about the open ocean because the open ocean has low levels of nutrients. most of the photosynthetic activity on earth occurs in the open ocean within the photic zone. organisms in the deep ocean are exposed to frigid temperatures and total darkness but it does not begin at the low-tide mark.