Which of the following are true of CFCs (chlorofluorocarbons)?
I) The EPA created a worldwide ban of the use of CFCs in aerosol cans in the late 1970s.
II) CFCs can be used as coolants and propellants in aerosols, refrigerators and air conditioners.
III) CFCs can occur naturally in the troposphere but do not occur naturally in the stratosphere.
IV) CFCs are nonflammable, nontoxic molecules that contain chlorine and fluorine atoms.