The correct option is D Montreal Protocol
The Montreal Protocol (1987) is a treaty to control the emission of ozone depleting substances such as CFCs.
The Geneva Protocol (1925) prohibited the use of toxic gases and biological methods of warfare.
The Kyoto Protocol (1997) aimed to reduce the emission of greenhouse gases such as carbon dioxide.
The Gothenburg Protocol (1999) is a multi-pollutant protocol to reduce all kinds of pollution by defining permissible limits of emissions of harmful gases such as sulphur dioxide, nitrogen oxide, ammonia, etc. that are released in the environment.