Consider the following: 1. Aerosols 2. Foam agents 3. Fire retardants 4. Lubricants. In the making of how many of the above are hydrofluorocarbons used?

1. Aerosols – Correct. HFCs are used as aerosol propellants in sprays and medical inhalers.

2. Foam agents – Correct. HFCs are used as foam-blowing agents in the manufacture of insulating and packaging foams.

3. Fire retardants – Correct. HFCs/related fluorinated compounds have been used in fire protection and fire suppression systems as halon substitutes.

4. Lubricants – Correct. HFCs are also used in the production of fluorinated lubricants/specialty lubricants, especially for refrigeration and industrial applications.

Hence, all four are correct, so the answer is (d).