None of the bove. Soil erosion occurs due to deforestation, water, wind and tillage of the land farms. It is the removal of the top layer of the soil, and leads to poorer quality of soil, called a soil disruption. This can be avoided by using proper farming techniques and afforestation.
Answer: b. Nitrogen; Oxygen
Explanation:
The air is a mixture of gases in the following percentage;
Nitrogen; 78%
Oxygen : 21%
Carbon(IV)Oxide : 0.03%
Argon : 0.9%
Others ( minute traces of Neon, Helium, Methane e.t.c) : 0.17%
Somewhat met in the nature