![](https://static.youtibao.com/asksite/comm/h5/images/m_q_title.png)
Weon the moon as we do on the earth iftllere were air and water on it. A.can live
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
![](https://static.youtibao.com/asksite/comm/h5/images/solist_ts.png)
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
When we were children, we were told that the moon () round the earth.
A.moved
B.had moved
C.moves
D.move
A.two million
B.300,000
C.480 times 300,000
D.400,000
A.it is four years that the light we can see will reach us
B.it will be brighter than the moon
C.we cannot tell whether or not it still exists
D.we will notice hat it is‘not moving
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.
Perhaps the best way to think of our present situation is to imagine a train coming into a switchyard. All of the switches are set before the train arrives, so that its path is completely determined. Some switches we can see, others we can not. There is no ambiguity if we can see the setting of a switch: we can say with confidence that some possible futures will not materialize and others will. At the unseen switches, however, there is no such certainty. We know the train will take one of the tracks leading out, but we have no idea which one. The unseen switches are the true decision points in the future, and what happens when we arrive at them determines the entire subsequent course of events.
When we think about the future of the universe, we can see our "track" many billions of years into the future, but after that there are decision points to be dealt with and possible fates to consider. The goal of science is to reduce the ambiguity at the decision points and find the true road that will be followed.
According to the passage, it is difficult to be certain about the distant future of the universe because we ______.
A.have too many conflicting theories
B.do not have enough funding to continue our research
C.are not sure how the universe is put together
D.have focused on investigations of the moon and planets
When we think about the future of the universe, we can see our "track" many billions of years into the future, but after that there are decision points to be dealt with and possible fates to consider. The goal of science is to reduce the ambiguity at the decision points and find the true road that will be followed.
According to the passage, it is difficult to be certain about the distant future of the universe because we______.
A.have too many conflicting theories
B.do not have enough funding to continue our research
C.are not sure how the universe is put together
D.have focused our investigations on the moon and planets
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
It can be concluded from this article that the attraction of the sun is ______.
A.more than half that of the moon
B.more than that of the moon
C.more than twice that of the moon
D.half that of the moon