2013年职称英语卫生类概括大意练习试题7_第2页

　　B Highway Police

　　C Working Principles

　　D Early Use of "Radar"

　　E Useful Tools

　　F Discovery by Chance

　　27 Echo-sounding devices were early used to

　　28 Ultrasonic device were used to

　　29 Police use radar on highways to

　　30 Radar helps pilots to

　　A detect nearby objects

　　B determine the depth of the ocean water

　　C decide how fast you drive

　　D stop passing ships

　　E map the ocean floor

　　F observe water flow