EXPLANATION
GS13. What is the main component of the Earth's atmosphere?
a) Nitrogen
b) Oxygen
c) Carbon dioxide
d) Water vapor
ANSWER: a) Nitrogen
EXPLANATION:
The main component of the Earth's atmosphere is a) nitrogen. It makes up about 78% of the atmosphere. Oxygen is the second most abundant gas, making up about 21% of the atmosphere. Carbon dioxide is the third most abundant gas, making up about 0.04% of the atmosphere. Water vapor is the fourth most abundant gas, but its concentration varies greatly depending on the weather.
