The correct answer is A. Methyl Isocyanate.
Methyl isocyanate (MIC) is an extremely toxic chemical that was used in the production of pesticides at the Union Carbide India Limited (UCIL) plant in Bhopal, India. On December 2, 1984, a leak of MIC from the plant killed an estimated 22,000 people and injured over 150,000 others. It is considered to be one of the worst industrial disasters in history.
Benzene hexachloride (BHC) is a chlorinated hydrocarbon that is used as a pesticide. It is a colorless, oily liquid that is highly toxic to humans. BHC was once widely used in agriculture, but it has been banned in many countries due to its toxicity.
Trinitrotoluene (TNT) is a yellow, crystalline solid that is used as an explosive. It is a highly toxic chemical that can cause cancer. TNT was used extensively in World War I and World War II.
Neither BHC nor TNT were involved in the Bhopal gas tragedy. The only chemical that was responsible for the disaster was methyl isocyanate.