Aerial photo taken on Nov. 16, 2021 shows staff preparing the tracks at Yunding Ski Resort in Chongli of Zhangjiakou City, north China's Hebei Province. The seats of Yunding Ski Resort in Zhangjiakou competition zone have been installed, and the staff are busy preparing the tracks for the upcoming test events of the Beijing 2022 Olympic Winter Games. [Photo by Wu Diansen/Xinhua]