Answer:
D. troposphere; stratosphere
Step-by-step explanation:
The ozone layer is a region in the upper part of the earth that is rich in ozone content (three molecules of oxygen or trioxygen O3). This layers extends as a blanket over the earth's globe as it absorbs the dangerous ultraviolet radiation from the sun preventing it from reaching the earth surface.
Ozone is a potential air pollutant when found in the ground level of the earth, the troposphere. It causes greenhouse gases, contributes to climate change and global warming threatening the health of living things at this region. However, Ozone is useful in the stratosphere where it helps in trapping incoming radiation from the Sun that would have been harmful to life on the earth.