why is it harder to breathe when climbing up a high mountain
A. the air compresses the lungs
B. the air has more moisture
C. the air pressure increases
D. the air is thinner
D. the air is thinner
As elevation increases, the air becomes thinner, meaning there is less oxygen available for the lungs to take in. This can lead to difficulty breathing and can make physical exertion, such as climbing a mountain, more challenging.