31.
This holds a planet's atmosphere close to its surface:

32.
During the afternoon the greatest temperature difference between the surface air and the air several meters above occurs on a:

33.
Ideal conditions for a strong radiation inversion:

35.
In a photochemical smog, which gas is an eye and mucous membrane irritant?

36.
_________ element had guided the earlier navigators to keep them on right path.

37.
Heat is energy in the process of being transferred from:

38.
Which one is true?

39.
A population is a group of

40.
Rising air cools by this process: