Which of the following pairs is/are correctly matched?

All are correctly matched

The answer is (4) All are correctly matched.

CCl₄, Fire extinguisher: Carbon tetrachloride (CCl₄) was once used as a fire extinguisher under the name pyrene. However, it is no longer used as a fire extinguisher because it is a toxic and harmful substance.

CCl₃NO₂, chloropicrin: Chloropicrin is a colorless, highly toxic liquid with a strong, pungent odor. It is used as a war gas and as a fumigant.

CFCl₃, Freon-II: Freon-II is a colorless, non-toxic gas that is used as a refrigerant and as a propellant in aerosol cans.

Therefore, all of the pairs are correctly matched.