Bhopal Gas Tragedy was caused due to the leakage of:

The correct answer is A) Methyl Isocyanate (MIC). On the night of 2-3 December 1984, a large volume of MIC escaped from the Union Carbide India Limited pesticide plant at Bhopal, which made carbaryl (Sevin). Water entered a storage tank, set off a runaway reaction, and the gas spread over the densely populated areas around the plant.

• B) Nitrogen dioxide is wrong. It was not the leaked agent in this disaster.
• C) Sulphur dioxide is wrong. It is a classic industrial pollutant linked to smog and acid rain, but it was not the Bhopal gas.
• D) Carbon monoxide is wrong. Many victims were harmed by the MIC and its reaction products, not by CO as the primary agent.

The core concept is industrial disaster and chemical safety. Mains often asks about the lessons of Bhopal: process safety management, the Factories Act, the Environment Protection Act 1986 (enacted after the disaster), the Bhopal Gas Leak Disaster (Processing of Claims) Act 1985, and the 1989 settlement. These connect to the polluter-pays principle and to the Disaster Management Act 2005.

Trap: aspirants pick carbon monoxide because it is the best-known toxic gas. Remember the specific chemical: MIC.