When CFCs are exposed to high levels of UV radiation, what occurs? A. The compound breaks down into nitric oxide and ozone. B. All of these C. A chlorine breaks off and forms a free radical. D. They become ionized and stick together in clumps that become part of smog.

C. A chlorine breaks off and forms a free radical

Explanation:

When CFCs are exposed to high levels of UV radiation in the atmosphere, the CFC molecule breaks into chlorine and forms free radicals.

These free chlorine radicals then reacts with ozone molecules and breaks the ozone atom (O3) to form chlorine monoxide and oxygen (O2) molecule.

CFCs are main cause of ozone depletion in the atmosphere.

Hence, the correct option is "C".