The correct answer is Alessandro Volta.
Alessandro Volta was an Italian physicist and chemist who is considered to be one of the pioneers of electricity. He is best known for his invention of the voltaic pile, which was the first battery. Volta also discovered that methane mixture with air could be exploded using an electric spark.
William Thomson, also known as Lord Kelvin, was a Scottish physicist and engineer who is considered to be one of the most important figures in the history of physics. He is best known for his work on thermodynamics, electricity, and magnetism. Thomson did not isolate methane gas.
Luis Pasteur was a French chemist and microbiologist who is considered to be one of the most important figures in the history of science. He is best known for his work on fermentation, pasteurization, and vaccines. Pasteur did not isolate methane gas.
William Crookes was an English physicist and chemist who is best known for his work on cathode rays and the discovery of the element thallium. Crookes did not isolate methane gas.