填空题
- 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
填空题
Echo-sounding devices were early used to 1.
填空题
Ultrasonic device were used to 1.
填空题
Police use radar on highways to 1.
填空题
Radar helps pilots to 1.