The correct answer is D. Methane.
Methane is a colorless, odorless gas that is lighter than air. It is the principal component of natural gas and is also produced by the decomposition of organic matter. Methane is highly flammable and can cause explosions in coal mines.
Carbon dioxide is a colorless, odorless gas that is heavier than air. It is produced by the combustion of carbon-containing materials, such as coal, oil, and natural gas. Carbon dioxide is not flammable and does not cause explosions in coal mines.
Nitrogen is a colorless, odorless gas that is the most abundant gas in the atmosphere. It is not flammable and does not cause explosions in coal mines.
Butane is a colorless, flammable gas that is heavier than air. It is used as a fuel in lighters and stoves. Butane can cause explosions in coal mines if it is mixed with air in the right proportions.
In conclusion, the gas that causes explosion in coal mines is methane.