Question

which system monitors carbon dioxide levels in the blood?
a the respiratory system
b the excretory system
c the gas system
d the endocrine system

Explanation:

The respiratory system is responsible for gas - exchange. It takes in oxygen and expels carbon dioxide. It monitors and adjusts carbon dioxide levels in the blood to maintain proper pH and homeostasis. The excretory system deals with waste elimination like urine, the term "gas system" is not a standard physiological system, and the endocrine system regulates body functions through hormones.

Answer:

A. the respiratory system