Which of the following protocols did aim for reducing emission of chlorofluorocarbons into the atmosphere?

Correct option is A. Montreal Protocol. To control the deleterious effect of the stratospheric ozone depletion an international treaty was signed at Montreal, Canada in 1987. It is popularly known as Montreal protocol. The protocol aimed at reducing the emission of chlorofluorocarbons into the atmosphere. So, the correct answer is 'Montreal protocol'.