由北京燕山石化（集团）公司研制生产的无铅清洁汽油，日前由其炼油事业部推向市场。这种汽油的投用将有助于降低汽车油耗，改善汽车尾气排放，减少环境污染。据调查，北京市大气污染的主要原因是机动车数目增长过快，因此，北京市规定1999年在北京市场销售的轻型汽车必须加净? The lead-free clean gasoline developed and manufactured by Beijing Yanshan Petrochemical (Group) Company has been pushed to the market by its refining department recently. The use of this gasoline will help reduce fuel consumption, improve vehicle emissions and reduce environmental pollution. According to the survey, the main reason for the air pollution in Beijing is that the number of motor vehicles has increased too fast. Therefore, Beijing Municipality must make the light vehicles sold in the Beijing market in 1999 must add net?