Question

atmosphere structure
troposphere and stratosphere
what is one of the characteristics of the troposphere?
low air pressure
presence of the ozone layer
high density of air molecules

Explanation:

The text states that the troposphere is the layer closest to the Earth's surface and is characterized by its high density of air molecules. The ozone layer is in the stratosphere. Air pressure is higher in the troposphere compared to higher - altitude layers.

Answer:

high density of air molecules