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 cycle
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
A new kind of tool has come into people’s view since 1960, that is, the silicon chip a small chip of silicon crystal. It is a bit (47) than a fingernail, but it is able to (48) several million "bits" of information or so. No doubt that it is an (49) brain.
Each year these chips grow cleverer, however (50) size becomes smaller, what’s more, their cost gets (51) .
It is (52) over two million years that human beings used chips, but human (53) changed so little at that time. Now we have made use of silicon chips for merely (54) years, but our life is changing faster with each passing day.
(55) will human life be like in two decades
Long long ago mankind began to use tools. Throughout the world, you can still find the tools which were used over two million years ago. People made such tools by hitting one stone (36) ano
A. less
B. more
C. most
D. correct
A new kind of machine (21) to take the place of humans. These machines (22) do jobs that are too dangerous for humans. (23) , they are being developed to work in nuclear power centers, deep waters and outer space.
This is how the new machines work. A machine (24) placed in an area far away from the person who controls it. The person wears a special hard bat with tiny television screens. The screens (25) the person see and hear exactly what the machine is (26) and hearing. This gives the person the feeling of being in the same place (27) the machine. The person controls the machine. The machine (28) the person’s movements exactly. If the person raises his right arm, the machine raises the right arm, too. This means an (29) worker can do a dangerous job while (30) in a safe place. For example, a person can direct the machine (31) a bomb (32) going near the bomb himself.
The new
A. like
B. resemble
C. as
D. the same
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