题目

请阅读下面一篇短文，并按照要求用英语写一篇 150 词左右的文章。 He Really Loved His Job Zhang Chao joined the PLA Navy in 2004 after graduating from a middle school in Yueyang, Hunan Province. He trained as a fighter jet pilot for five years and in 2009 he joined a naval aviation squadron(海军航空兵), because flying a J­15 above the carrier was Zhang Chao's biggest wish. In March last year, Zhang passed the strict selection procedures and became a pilot in the carrier­based(舰载的) aviation force. Unfortunately, however, when landing after a routine t如图（甲），水平地面上有一面积为30πcm2的灰色扇形OAB，且半径OA与地面垂直．若在没有滑动的情况下，将图（甲）中扇形，按图（乙）所示的方式从左向右滚动至OB垂直地面为止，并发现O点移动距离恰好为10πcm，则扇形OAB的半径长A.πcmB.3cmC.6cmD.cm