Why is it harder to breathe when climbing up a high mountain?
○ The air is thinner.
○ The air compresses the lungs.
O The air has more moisture.
○ The air pressure increases.
The correct answer is: The air is thinner.
At higher altitudes, the air pressure decreases, which means there are fewer oxygen molecules in the air. This can make it harder for the body to take in enough oxygen with each breath, leading to difficulty breathing.