Passage III
Cloud cover is the percent of Earth's surface covered by clouds. Cloud cover may increase because of an increase in the cosmic ray flux (number of high-energy particles from space reaching Earth per m2 per hour). Table 1 shows how Earth's cover of low clouds (0 km to 3.2 km altitude) varies with the cosmic ray flux. Figures 1−3 show the relative cosmic ray flux, RCRF (the percent below the flux measured on October 1, 1965), and the monthly average cover of high clouds (6.0 km to 16.0 km altitude), middle clouds (3.2 km to 6.0 km altitude), and low clouds, respectively, from January 1980 to January 1995.
17. High clouds are composed primarily of ice crystals, whereas low clouds are composed primarily of water droplets. This difference is most likely because the average air temperature at altitudes from:
Your Answer is
Correct Answer is D
Explanation
General knowledge questions.
The higher the altitude, the lower the temperature (for the troposphere)