[单项选择]Whether there is sufficient nitrogen on Mars is important because it ______.


A. can raise the temperature of Mars
B. can protect living beings from harmful rays
C. can change the atmosphere of Mars
D. is an important part of the air people breathe

[单项选择]Whether there is sufficient nitrogen on Mars is important because it ______.


A. can raise the temperature of Mars
B. can protect living beings from harmful rays
C. can change the atmosphere of Mars
D. is an important part of the air people breathe

[单项选择]When will people probably be able to live on Mars


A. In 200 years.
B. In 10,000 years.
C. In 100,000 years.
D. Unknown.

[单项选择]At the first sight the planet Mars does not appear very welcome to any kind of life. It has very little oxygen and water, the temperature at night is below 50℃ and winds of 100 miles per hour cause severe dust storms. However, the surface of the planet seems to show that water flowed across it some time in the past, and it is believed that there is enough ice at the poles to cover the planet with water if it melts. Although there is no life on the Mars now, some scientists think that there may have been some form of life long time ago. At that time, the planet had active volcanoes; the atmosphere was thicker and warmer; and there was water. In fact, in some ways the Mars may have been similar to the Earth, where life exists. Some people believe that the Mars could support life in the future if the right conditions were produced. The first step would be to warm the planet using certain gases which trap the Sun"s heat in the planet"s atmosphere. With warmth, water and carbon dioxide(二氧化碳), simple plants could begin to grow. These plants could slowly make the Mars more suitable for living. It is estimated that the whole process might take between 100,000 and 200,000 years. In the meantime, people could begin to live on the planet in special closed environments. They would provide a lot of useful information about conditions on the Mars and the problems connected with living there.Some scientists think there may have been life on the Mars in the past because ______.
A. there is no life there now
B. there is a large amount of water at the poles
C. the Mars may be able to support life in the future
D. conditions may have been similar to those on the Earth

[填空题]There have been claims that warming on Mars and Pluto are proof that the recent warming on Earth is caused by an increase in solar activity, and not by greenhouses gases. But we can say with (47) that, even if Mars, Pluto or any other planets have warmed in recent years, it is not due to (48) in solar activity.
The Sun’s energy output has not increased since direct (49) began in 1978. If increased solar output really was (50) , we should be seeing warming on all the planets and their moons, not just Mars and Pluto.
Our solar system has eight planets, three dwarf planets and quite a few moons with at least a (51) atmosphere, and thus a climate of sorts. Their climates will be 52 by local factors such as orbital variations, changes in reflectance (反射率) and even (53) eruptions, so it would not be surprising if several planets and moons turn out to be warming at any one time.
However, given that a yea

[单项选择]This information is not sufficient by itself to prove your argument but it may be used as __________. evidence.


A. subtle
B. subsidiary
C. substantial
D. subjective

[单项选择]He has sufficient time to finish the task.
A. perfect
B. adequate
C. great
D. limited

[单项选择]According to the Mars Theory, why does the moon contain little iron

[单项选择]Scientists are interested in Mars because ______.


A. people might have to migrate there someday
B. people could live there naturally
C. life has ever existed there
D. its atmosphere is quite different

[单项选择]Commodity inspection certifies whether the quality, quantity and the packing of the goods are in compliance ______ the contract requirements or not.
A. to
B. with
C. of
D. that