Where is the atmosphere the most dense?

A. The coldest part

B. The top

C. The bottom

D. The warmest part

Nearly all atmospheric water vapour or moisture is found in the troposphere. The troposphere is the layer where most of the world's weather takes place. Since temperature decreases with altitude in the troposphere, warm air near the surface of the Earth can readily rise, being less dense than the colder air above it. So, I'm pretty sure he answer would be the coldest part.

Answer: The bottom is the right one.

The troposphere is what contains 80% of the mass of the atmosphere and is where all the weather stuff happens.