Environmental stresses at high altitudes include
a. increased temperatures.
b. lower humidity.
c. decreased uv radiation.
d. quick ascent.

the answer is B. lower humidity  because People have the misconception that a high humidity means it is hot, sultry and muggy. However, mostly the opposite is the case. As temperatures fall the relative humidity normally rises because the amount of water vapor in the air is mostly reasonably constant and air at lower temperatures holds less water vapor.

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