How are reflecting telescopes similar to devices that produce laser light?

A: Both use crystals to produce a beam of light.
B: Both have convex lenses that magnify objects.
C: Both have concave lenses that magnify objects.
D: Both use mirrors to reflect a beam of light.

Assume that a person skiing high in the mountains at an altitude of h = 15100 ft takes in the same volume of air with each breath as she does while walking at sea level. determine the ratio of the mass of oxygen inhaled for each breath at this high altitude compared to that at sea level. assume that the air composition (i.e. % of air that is oxygen) is the same at sea level as it is at 15100 ft.