Probably at that time, several pure science students and two liberal arts students had a barbecue together, and they made it themselves. Then the charcoal won't light. The science students poured oil and alcohol on the charcoal, but it still didn't light. Then they called their classmate's father and asked him to light charcoal with natural gas. The first reaction of several science students at that time was that the chemical formula CH4 of natural gas, also known as methane, was flammable. Please check before use, otherwise it will cause explosion and the risk factor is high. At that time, we were still thinking about how to ignite charcoal safely with natural gas. Then two liberal arts students silently put charcoal on the gas stove, opened the fire and lit it.