雷达在海洋运输中发挥着重要的作用,某海岛雷达向远处停泊的油轮发出一束电磁波,从发出到接收共用时10-4s,则该油轮距雷达 ____ km.
下列工程中,属于为解决我国区域之间能源分布差异而实施的是( )
Tony knows China very well because he ______ in China for twenty years.