阅读理解。
Sometime early in the next century, human beings will move to Mars. They will live
there for about a year, and then will be replaced with another group of pioneers. Building
the base on Mars will advance our knowledge of the solar system and aid in our
understanding of the earth.
We already know that Mars resembles the earth in many aspects : general size,
presence of water, lengthof day, range of temperatures. These resemblances have
caused many people to consider a centuries-long project: to transform Mars.
Transforming means alterinB a planet's surface so that the Earth's life forms can
survive there. This concept, previously found only in science fiction is now being
seriously considered by scientists.
Transforming Mars is theoretically simple : add nitrogen (氮气)and oxygen to the
atmosphere; pump water to the surface; and add the earth's plants and animals in the
order in which they developed on the Earth. But it will take at least 300 years.
Some people think that such a project is too huge for humans to undertake, but
there are very good reasons to make the attempt. The earth now contains some 6
billion people and no one has any idea of how many humans the earth can support.
Our very existence and numbers are threatening many other species. We also have
had some experience with transforming our own planet : altering thelandscape ,
theatmosphereand the climate. Currently transforming earth has become a wiser activity
as we try to control global warming, air and water pollution, and' preserve some natural
living places.
While the possibility of such a project is small, it is not impossible. Even if earthbound
societies come and go in the next 300 years, the project can continue through the work
of the Mars settlers without the need for constant backing from the earth.
The future existence of all the people in our world may very well depend upon our ability
to transform Mars.
1. What does the underlined word " altering"mean in the second paragraph?_______
A. Warming.
B. Changing.
C. Planting.
D. Building.
2. According to the passage the main purpose of transforming Mars is to._______
A. do some scientific research work
B. find out its similarity to the Earth
C. avoid the dying way of many other species
D. find on Mars living place for the increasing human beings
3. The main reason for causing many people to consider transforming Mars is that._______
A. there are some resemblances between the Earth and Mars
B. transforming Mars is theoretically simple
C. our existence and numbers are threatening many other species
D. the development of science and technology is very rapid
4. What's the author's attitude towards the project?______
A. Optimistic.
B. Negative.
C. Sceptical(怀疑的 ) .
D. Objective.
