While all my classmates seen 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 sometime before the end of the century, there will be a human colony on Mars. It will happen when people finally realize that tow-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 on another world. Enough supplies can be sent on ahead. And every two years more supplies and more people will needs, and Mars is far more pleasant than the other planets in the outer space. Paul Davies. USA Paul Davies points out that  _  .
humans need only a one-way ticket to Mars. two-way trips to Mars will be made safe soon it is easy to reduce the danger and cost of flights to Mars it is cheap to build an everlasting human settlement on Mars
Question: While all my classmates seen 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 sometime before the end of the century, there will be a human colony on Mars. It will happen when people finally realize that tow-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 on another world. Enough supplies can be sent on ahead. And every two years more supplies and more people will needs, and Mars is far more pleasant than the other planets in the outer space. Paul Davies. USA 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
Answer: