Which of the following chemicals replaced chlorofluorocarbons (CFCs) after their phase-out due to the Montreal Protocol?

Hydrochlorofluorocarbons were introduced as transitional replacements for chlorofluorocarbons after the Montreal Protocol.

Perfluorocarbons are potent greenhouse gases used elsewhere, not the direct ozone-era substitutes.

Sulphur hexafluoride is an extremely strong greenhouse gas, not a chlorofluorocarbon replacement.

Halons are themselves ozone-depleting fire suppressants being phased out, not the substitutes.

The interim replacements were the hydrochlorofluorocarbons, which harm ozone far less.

These are in turn being replaced by hydrofluorocarbons and newer low-impact refrigerants.