Answer:
When CO2 is breathed into the lungs, it dissolves in the water there, diffuses across the alveolar-capillary membrane, and enters the bloodstream. As it combines with water, it forms carbonic acid, making the blood acidic. So CO2 in the bloodstream lowers the blood pH.
a cell adapts using natural celection in the long term
in the short term, look at this Wikipedia article.
https://en.wikipedia.org/wiki/Cellular_adaptation
The answer would be B i believe<span>(a protease) begins the chemical digestion of protein</span>
