The 1984 Bhopal gas tragedy was caused by methyl isocyanate (MIC) gas leakage from a Union Carbide pesticide plant. Option C says 'methyl isocynide' which appears to be a typo for methyl isocyanate. This was one of the world's worst industrial disasters, exposing over 500,000 people to toxic gas. The other options (carbon dioxide, sulfur dioxide, ozone) are incorrect - they are common gases but not involved in this specific disaster.