The Miller-Urey experiment in 1953 simulated early Earth's atmosphere with a gas mixture of hydrogen (H\(_2\)), methane (CH\(_4\)), and ammonia (NH\(_3\)) in a 2:1:1 ratio. Electrical discharges mimicked lightning. This process generated amino acids and other organic compounds. Therefore, the correct ratio is 2:1:1 (H\(_2\): NH\(_3\): CH\(_4\)).