题目内容：

While all my classmates seem to be crazy about a one-way ticket to Mars, I'd rather say Mars is totally unsuitable for human existence. People won’t have enough food supplies there, and the terrible environment would make it impossible for them to live a long life. Besides, the journey won't be safe. Can anybody explain to me just why people would go to Mars, never to return?  Steve Minear, UK

Here are the things you can think of: the desire to explore a foreign and unique environment, the excitement of being the first humans to open up a new world, the expectation of fame and glory┅. For scientists there is another reason. Their observations and research will probably lead to great scientific achievements.  Donal Trollop, Canada

There are already too many people on the Earth. I think that something before the end of the century, there will be a human colony on Mars. It will happen when people finally realize that two-way trips to the red planet Mars are unnecessary. Most of the danger of space flight is in the launches and landings. Cutting the trip home would therefore reduce the danger of accidents, save a lot of money, and open the way to building an everlasting human settlement in another world. Enough supplies can be sent on ahead, and every two years more supplies and more people will be sent to the new colony. Mars has all the materials for a colony to produce or make everything it needs, and Mars is far more pleasant than the other planets in the outer space.   Paul Davies, USA

1.The main purpose of Steve Minear's writing is_________.    .

    A. to report his classmates' discussion    B. to invite an answer to his question

C. to explain the natural state of Mars    D. to show his agreement on going to Mars

2.Which of the following best states Donal Trollop's ideas?  

    A. There is a plan to send humans to Mars

B. There are many reasons for going to Mars

 C. Scientists become famous by doing research on Mars 

D. It is possible to build an Earth-like environment on Mars

3. Paul Davies points out that______.  

    A. humans need only a one- way ticket to Mars    

    B. two-way trips to mars will be made safe soon

    C. It is easy to reduce the danger and cost of flights to Mars

    D. It is cheap to build an everlasting human settlement on Mars

4.What does Paul Davies think of human existence on Mars? 

    A. Humans will have to bring all they need from the earth

    B. Humans will find Mars totally unsuitable for living

    C. Humans can produce everything they need

    D. Humans can live longer in the colony on Mars