One of the atmospheric layers was created by living things to help keep living things alive. What is that layer? * exosphere
*tropopause
*ozone
*thermosphere

Troposphere

Explanation: The Troposphere: The Layer in Which We Live

The lowest layer of the atmosphere, which lies next to the

Earth’s surface, is called the troposphere. The troposphere is also

the densest atmospheric layer. It contains almost 90% of the

atmosphere’s total mass! Almost all of the Earth’s carbon dioxide, water vapor, clouds, air pollution, weather, and life-forms

are in the troposphere. As shown in Figure 4, temperatures vary

greatly in the troposphere. Differences in air temperature and

density cause gases in the troposphere to mix continuously.

just finished the test, the answer is d, greg is the least cost-effective because he charges the most for the project

when it is at an intermediate population density