The cells that make up a human body need oxygen at all times. During periods of exercise and activity, the amount of oxygen need
ed increases. To meet this increased need, the number of breaths per minute during exercise can be sharply higher than the number of breaths per minute while at rest. Which term BEST describes the process by which cells work together to maintain the needed level of oxygen? A) homeostasis
B) metabolism
C) osmosis
D) respiration
