The correct answer is D. acetylene.
When water is poured on calcium carbide, a chemical reaction occurs to produce acetylene gas and calcium hydroxide. The reaction is as follows:
$$CaC_2 + 2H_2O \to C_2H_2 + Ca(OH)_2$$
Acetylene is a colorless, flammable gas with a garlic-like odor. It is used in welding, cutting, and other industrial applications. It is also used as a fuel in some internal combustion engines.
Methane, ethane, and ethylene are all hydrocarbons. Methane is the simplest hydrocarbon, with the chemical formula CH4. It is a colorless, odorless gas that is the main component of natural gas. Ethane is a two-carbon hydrocarbon with the chemical formula C2H6. It is a colorless, flammable gas that is used as a fuel and in the production of other chemicals. Ethylene is a three-carbon hydrocarbon with the chemical formula C2H4. It is a colorless, flammable gas that is used in the production of plastics, rubber, and other chemicals.
When water is poured on calcium carbide, the reaction that occurs produces acetylene gas, not methane, ethane, or ethylene.