Question

regulates the volume of water in the blood and also has an important role in eliminating wastes.
a excretory system
b nervous system
c respiratory
d endocrine system

Explanation:

The excretory system filters the blood, regulates water - volume in blood and eliminates waste products. The nervous system controls and coordinates body functions, the respiratory system is for gas - exchange, and the endocrine system regulates body processes through hormones.

Answer:

a. Excretory system