An international conference in this city called for a reduction in cfc emissions worldwide.

barcelona
madrid
montreal
peking

The right answer is The Montreal Protocol.

Chlorofluorocarbons (CFCs) and certain other substances were leaked into the atmosphere throughout their production and use, breaking down ozone molecules that form in the stratospheric layer and absorb much of the ultraviolet radiation that reaches the Earth. This ozone depletion was shown to have serious health and environmental consequences for human skin and eyes, crops and marine life.    As a result, in 1987, world leaders signed the Montreal Protocol, a global agreement for the phase‐out of production of ODS. Since that time, continued scientific study has led to the strengthening of this protocol, which has now been ratified by 196 countries.

yup! you are correct it is b.

idk lol i just wanna finish mines