HElP PLZZ... EMERGENCY?

Question

can sombody please help me answer these questions for earth science... please im close to failing.

1.what makes up from 0 to 4 percent of the atmoshpere?

2.what contains 75 percent of the atmospheric gases?

3.cold air is denser than warm air and therefore has higher_______

4.what is the only substance that exists as a solid,liquid,and a gas in earths atmosphere?

Answer 1

1.  I'm not sure

2.  Nitrogen

3.  Density

4.  Water

Answer 2

1. Various trace gases

2. Troposphere

3. Refractive index

4. Water