By Muyu Xu and David Stanway ZHANGJIAKOU, China (Reuters) – China is using the Winter Olympic Games to drive its efforts to improve the environment, but smog-prone capital Beijing is still preparing for the worst as the opening ceremony looms. Beijing has improved its air quality since China won its bid to host the Games, but the Ministry of Ecology and Environment has said winter smog risks remained “severe”. Ministry spokesman Liu Youbin told reporters on Thursday that contingency plans were in place. “When the time comes, Beijing and Hebei will be guided to adopt reasonable environmental pr…