题目内容
（请给出正确答案）
By moving the radar beam around slowly in circles, we can ______ the surroundings.
A．explore
B．expose
C．exploit
D．expand
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Some researchers recently have studied the eyes of the common frogs and have discovered that a frog's eyes only find moving things such as insect-shaped objects and large, threatening objects. As a result of studying the eyes of frogs, scientists have constructed a simple electronic model of a frog's eyes which can track airplanes circling above an airport and then provide information to computer-run air traffic control systems. Someday such electronic eyes may provide the means to automatically guide automobiles by providing information about objects moving toward the automobile. Other scientists have studied the compound eyes of some insects and crabs and have built a seeing machine that is a simple model of the horseshoe crab eye.
The hearing of a number of creatures also has been studied extensively so that hearing machines can be developed. Bats have unusual hearing which can extend into the ultrasonic (超声的) range. The dolphin also has been studied extensively, and dolphins are able to navigate through water extremely effectively. Radar and sonar(声 纳) systems which are used to help ships and planes navigate have been based on the sonar systems of both bats and dolphins.
Which of the following could be the best title？
A．Electronic Eyes
B．The Science of Bionics
C．Sonar Systems
D．The Hearing of Some Creatures
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
Implied but not stated is that ______. ()
A．laser-doppler radar is more accurate than microwave radar
B．microwave radar may not ensure absolute precision in measuring varying speeds
C．the light-beam radar can measure only slow speeds with accuracy
D．microwave radar operates at a higher frequency than laser-doppler radar
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 easily detect and measure the movement of a vehicle edging up to a satellite space station. A control system using so precise a signal as this would allow a huge vehicle to dock at a space station as lightly as a feather.
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
An appropriate title for this passage would be ______. ()
A．Rendezvous in Space
B．Landing at a Space Station
C．New Radar for the Space Age
D．Space Navigation
A.want their pigeons to win the race
B.are sending radar signals to their pigeons
C.do not know whether the race began on time
D.do not trust the rules set down by the judges
Which of the following statements is not true according to the passage ______. ()
A．accuracy ill speed measurement is essential to spaceships
B．the speeds of space vehicles will vary
C．inaccuracies in measurement could cause accidents in space missions
D．a bump could affect the preciseness of the laser-doppler radar
A.going on
B.moving on
C.putting on
D.carrying on
A．to moving
B．to be moving
C．moving
D．be moving
People moving within country borders are often motivated by the desire to ______.
A．follow suit
B．live close to relatives
C．integrate themselves into the mainstream society
D．escape persecution
