Answer:
One Vacationing in high Colorado mountains
Explanation:
The difference in air pressure at two locations is felt when the oxygen concentration is different for these two locations. Â
In general the concentration of oxygen is the same for both the atmosphere above a plain land and above a sea. Therefore, the sister vacationing near sea will not face difficulty in breathing. Â
While the sister vacationing on mountains will feel air pressure difference due to a decreased oxygen concentration over mountains. Â