Laser-doppler radar （　）

A:makes use of microwaves B:measures the movements of a spaceship by means of light beam C:makes use of sound waves D:Both A and B

Laser-doppler radar ______. ( )

A:measures the movements of a spaceship by means of light beam B:makes use of microwaves C:makes use of sound waves D:Both A and B

Police use radar on highways to ______

Radar helps pilots to ______

What is the purpose of the radar reflector?

A:Making objects less visible B:Making echoes weaker on theradar C:Making large echoes smailer D:Making small objects bettervisible

"For navigationthe radar is ________．

A:of no value B:very important C:so expensive that people don't know how much it is D:valueless"

"Radar surveillance systems ________．

A:may provide all ships of their technical conditions B:should be installed with VHF C:shall be correctly interpreted D:are intended to smooth and control the flow of traffic to and from the harbor

Without doubt the radar is a highly important navigation aid. But duty officer shall aware that_____when using it.

A:Its range reading is more accurate than its bearing reading B:A low-lying coastline with a long, flat beach will show up properly on the radar C:Radar is only aimed at collision avoidance. D:The use of radar is necessary only when visibility is restricted."

______ is on the panel of radar．

A:KEYLOCK B:REPEATER C:STATIC INVERTER D:ANTI-CLUTTER-SEA"