_______ the moon moves round the earth is well known to all of us.A. ThatB. WhatC. WhenD
_______ the moon moves round the earth is well known to all of us.
A. That
B. What
C. When
D. As
_______ the moon moves round the earth is well known to all of us.
A. That
B. What
C. When
D. As
When we were children, we were told that the moon () round the earth.
A.moved
B.had moved
C.moves
D.move
We believe, however, that some two thousand million years ago, another star wandering through space, happened to come near our sun. Just as the sun and the moon raise tides on the earth, so this star must have raised tides on the surface of the sun. But they were very different from the small tides that are raised in our oceans; a large tidal wave' must have travelled over the surface of the sun, at last forming a mountain so high that we cannot imagine it. As the cause of the disturbance (动荡) came nearer, so the mountain rose higher and higher. And before the star began to move away again, its tidal pull had become so powerful that this mountain was torn to pieces and threw off small parts of itself into space. These small pieces have been going round the sun ever since. They are the planets (行星).
Millions of stars are______.
A.following a regular path in space
B.always travelling together
C.seldom wandering about in the universe
D.moving about without a fixed course
Weon the moon as we do on the earth iftllere were air and water on it.
A.can live
B.will live
C.lived
D.could live
You feel cool when you are near a lake or river because ______.
A.the water is cold
B.the earth is hot
C.the water is colder than the earth
D.cool air from the water moves towards the land
A.Studying the movements of the sun, moon and stars.
B.Studying the weather
C.Studying the movements of the earth
D.None of the above
A. principal B. basic C. initial D. elementary
Suppose a man wanted to reach a distant star. Even if he traveled his whole life, he would have to move faster than the speed of the light. Nothing can move that fast except light itself.
Strange things happen to an object when it moves rapidly. The object weighs more. An object moving at 86 percent of the speed of light is twice as heavy as it is at rest. A stick appears shorter. A clock runs more slowly. A man would not age so fast as he would on the earth.
Light travels more than 186,000 miles a second, or about 11 million miles a minute. In one year, light travels six trillion miles. That great distance is called a light-year. It is used to measure distance in space.
The star closest to our sun is Alpha Centauri. It is more than four light-years away. If one traveled at the speed of light, he could make a round trip to Alpha Centauri in nine years. But, even at that speed, he could not reach Alcaid (北斗星) in the handle of the Big Dipper. A one-way journey to Alcaid would take almost 200 years
1.In this passage the words “closest to our sun” means the star().
A、the earth we live on
B、Alpha Centauri
C、the Big Dipper
D、the moon
2.A one-way journey to Alcaid would take().
A、about nine years
B、less than four years
C、almost 200 years
D、less than 100 years
3.Why do we measure the distance in light-years instead of miles?()
A、Units of light-years sound better.
B、Using light- years reduced the number of figures used.
C、We used to measure distance in light-years long ago.
D、We do not make mistakes when we use light-years.
4.If a stone moved at the speed of light, it().
A、would weigh twice more than it is motionless
B、would weigh as much as it is on earth
C、would weigh less than it is on earth
D、would not have weight at all
5.This story is mainly about ().
A、the distance between the sun and the other stars
B、the problems of traveling to faraway stars
C、what happens when we travel faster than the speed of light
D、the tool we use when we go to faraway stars
Time can be defined in the following ways except _______.
A.the rise and fall of tides
B.an important victory in battle
C.the revolution of the moon around the earth
D.schedule of an business appointment
The journey to the moon has been the first step towards future explorations in space. The distance between the moon and the Earth is very short indeed when compared with the distances between Earth and the other planets. Mars, the nearest planet to Earth is of miles away ! Traveling to the planets or travels between planets will be man’ s next aim. Such travels will be more difficult than the trip to the moon and certainly more exciting.
Recently, two American unmanned spacecraft, Vikings 1 and 2, landed on Mars in an attempt to discover whether that planet had any life on it. So far the presence of life on Mars has neither been proved nor ruled out. Russian space-probes have discovered that the surface of Venus is so hot that it is almost certain that there is no life there. Also the atmosphere of Venus is extremely, dense and the pressure is nearly a hundred times greater than the pressure of the Earth’s atmosphere.
Scientists believe that in the future, space stations can be built in space. These stations can act as stop-over points in space. Spacecraft can refuel at these stations and get their supply of air, food and water.
Spaceships of the future will be bigger and faster. They will be able to carry passengers for trips to the moon or planets.
Man may in the future find planets which have the same conditions as those we have on Earth, and make them his home. However such a possibility is still in the distant future. At the same time, Man should realize that the Earth will be his only home for a long time and begin to value and care for it.
Which of the following statements is true?
A.Recently, two American astronauts have landed on Mars.
B.The surface of Mars is very hot.
C.The journey to the moon started the future exploration in space.
D.There is life in Venus.