Ozone in the upper atmosphere has been depleted by a. sulfur dioxide. b. chlorofluorocarbons. c. carbon dioxide. d. oxygen.

Ozone in the upper atmosphere has been depleted by chlorofluorocarbons.

Explanation:

The ultra-violet rays radiated by the sun break down the chlorofluorocarbons to release free chlorine atoms in the atmosphere. These free chlorine atoms react with oxygen from the ozone to form diatomic or molecular oxygen.

This process continues and further destroys the ozone layer resulting in its depletion. The ozone molecules are capable of keeping harmful UV rays away from the earth's atmosphere.

But the molecular oxygen fails to do that, thus allowing harmful UV rays to enter the earth's atmosphere.