The cardio-respiratory system consists of the cardio vascular system (heart and blood vessels) together with respiratory system (lungs and air ways). These systems work to transport oxygen to the muscles and organs of the body and remove waste products including carbon dioxide.
Hmm. Let's see. I don't think it's D. And recognizing sources in stress does help, but I think the first thing is knowing that someone has too much stress, so i think the answer is A.
