The gas responsible for most of the fatal explosions in coal mines isA. butaneB. etheneC. ethaneD. methane

The gas responsible for most of the fatal explosions in coal mines is D. methane.

Methane is a colorless and odorless gas that can accumulate in coal mines and create highly explosive conditions when mixed with air. This is primarily due to its flammability and the fact that it can form explosive mixtures with air in certain concentrations. Methane is often referred to as "firedamp" in the context of mining.

While butane, ethene, and ethane are also hydrocarbons, they are not typically found in significant quantities in coal mine environments nor are they as commonly associated with mine explosions as methane is. Hence, safety measures in coal mines focus significantly on monitoring methane levels to prevent potential disasters.