Question

ozone - depleting chemicals
the ozone layer is a crucial part of the stratosphere. it shields earth from harmful ultraviolet radiation. certain chemicals released at the earths surface can migrate up into the atmosphere, posing a threat to the ozone layer. scientists have noted increased ultraviolet radiation, resulting in ozone holes. research identified ozone - depleting chemicals like cfcs, hcfcs, and halons. these compounds often contain chlorine.
what happens when certain chemicals released at the earths surface migrate upward?
they improve air quality
they strengthen the ozone layer
they pose a threat to the ozone layer

Explanation:

The ozone - layer protects Earth from harmful ultraviolet radiation. Certain chemicals like CFCs, HCFCs, and halons released at the Earth's surface can migrate to the atmosphere and deplete the ozone layer, posing a threat to it.

Answer:

They pose a threat to the ozone layer