CFCs are safe on Earth's surface but become very destructive to ozone when exposed to UV light in the upper ? Upper what

CFCs are broken down by UV photolysis, but the process takes a long time since it takes decades to cycle all of the air in the troposphere through the upper stratosphere. ... The photolysis of CFCs generates a highly reactive chlorine atom that can attack ozone or form compounds that destroy ozone. upper stratosphere should be your answer

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

the answer is c.mitochondria. glad to .