32.
Water from springs contain dissolved __________ compounds which are used to cure some skin diseases.

33.
Which of the following is considered a variable gas in the earth's atmosphere?

34.
The limitating factor in temperate and boreal forest is

35.
Eutrophication of water bodies resulting to killing of fishes is mainly due to non-availability of

36.
The ozone at ground level is primarily from __________ precursors.

37.
Gas released during photosynthesis is

38.
The earth's first atmosphere was composed primarily of:

39.
Which gas is likely to be reduced in the atmosphere by deforestation?

40.
In a volume of air near the earth's surface, ____ occupies 78 percent and ____ nearly 21 percent.