[单项选择]

Passage two
A new kind of radar has been developed for space-age travelers. A working laboratory model of a new system of radar that makers use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that uses microwaves.
The model has shown that this radar system can measure with absolute precision speeds varying from spaceship orbital injection velocities 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 between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip(划破) 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 trillions(万亿) of cycles per second, could easily dete
A. is the first radar system to work in space
B. is more precise than microwave radar
C. is easier to operate than microwave radar
D. will work on the earth's surface as well as in space

[单项选择]

Passage two
A new kind of radar has been developed for space-age travelers. A working laboratory model of a new system of radar that makers use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that uses microwaves.
The model has shown that this radar system can measure with absolute precision speeds varying from spaceship orbital injection velocities 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 between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip(划破) 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 trillions(万亿) of cycles per second, could easily dete
A. are virtually negligible
B. cannot be detected visually
C. are of extremely high velocity
D. all of the above

[单项选择]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 trillions (百万兆) of cycles per second, could easi
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