What is A% and B% as depicted in the diagram showing the composition of the atmosphere

1. A: 72 B: 27
2. A: 77 B: 22
3. A: 78 B: 21
4. A: 79 B: 20

About 90 percent of air mass lies within about …………… from the earth's surface.

1. 20 km
2. 22 km
3. 25 km
4. 30 km

Mountain climbers set up camps at the base as well as at regular intervals along their climb. Why?

1. To acclimatize their bodies to lower concentration of air.
2. To acclimatize their bodies to lower temperature.
3. To acclimatize their bodies to pressure.
4. All of the above.

Assertion (A): The atmosphere is the most dynamic entity on the earth's surface.

Reason (R): Large masses of air are being moved up and down and across the surface of the earth.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R does not explain A.
3. A is true but R is false.
4. A is false but R is true.