[单项选择]Laser-dopple radar is especially valuable in space missions because it ______.


A. is one thousand times more precise than microwave radar
B. provides precise measures of the velocity of space vehicles
C. is a new system of radar
D. can measure the movement of a spaceship less accurately than a microwave radar

[单项选择]Laser-dopple radar is especially valuable in space missions because it ______.


A. is one thousand times more precise than microwave radar
B. provides precise measures of the velocity of space vehicles
C. is a new system of radar
D. can measure the movement of a spaceship less accurately than a microwave radar

[单项选择]Laser-doppler radar is especially valuable in space missions because ______. ( )
A. it is one thousand times more precise than microwave radar
B. it provides precise measures of the velocity of space vehicles
C. it is a new system of radar
D. it can measure the movement of a spaceship less accurately than a microwave radar

[单项选择]With the help of the space-shuttle-carried radar, archeologists found
A. a new stretch of the Sahara desert.
B. traces of ancient riverbeds under the Sahara Desert.
C. some traditional archeological tools in the Sahara Desert.
D. a mountain beneath the Sahara Desert.

[单项选择]All had to stay in the open space, especially at night, for the ______ of the warning of an earthquake.
A. donation
B. domination
C. destination
D. duration

[单项选择]Where does the Syrian radar station lies in


A. Hezbollah.
B. Jerusalem.
C. Central Baalbek.
D. Bekaa Valley.

[单项选择]US officials are concerned over this radar issue because ______.


A. they feel that this technology could post as a potential threat to the US
B. they are worried the new technology might be used against Taiwan
C. they fear that it might spark tension in the Taiwan Straits
D. this deal could trigger a new round of arms race around the world

[单项选择]The installation of radar is supposed to keep track of airlines in the __________.
A. velocity
B. proximity
C. terrain
D. vicinity

[单项选择]By moving the radar beam around slowly in circles, we can ______ the surroundings.
A. explore
B. expose
C. exploit
D. expand

[单项选择]

Passage Five
A new kind of radar has been developed for spaceship travelers. A working laboratory model of a new system of radar that makes use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that used microwaves.
The model has shown that this radar system, known as laser-doppler radar, can measure with absolute precision speeds varying from spaceship orbital injection (进入) velocities (速度) of five miles per second down to virtual stops--speeds of less than one ten thousandth of an inch per second. According to the scientists who are developing this system, such fine measures of velocity are of prime importance in space missions. In a rendezvous (对接) between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip open a ship’s skin, or a nudge could knock the station out of its orbit.
The light-beam radar, which operates at a frequency of t
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