What is the solar system? It is our sun and other     1     (planet) that travel around it. The sun is in the center of it and     2     (it) shape looks like an egg.

Our solar system including the Sun, the Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Our solar neighborhood is an     3     (excite) place. Most people think we have to live in outer space, although no one     4     (communicate) with us so far. One reason is that some of us can hardly live on the earth because of     5     (increase) population, and the other reason is that perhaps some     6     (science) will create some space like our earth for people     7     (live) in. Are you expecting that?

While others disagree with the ideas above. They believe we will like inner space better     8     (compare) to outer space in the future. We are not certain if we can live     9     (safe) in outer space because it is changing all the time. As a result, most people will refuse to live there.

Which one do you believe? I can’t wait     10     (know) your answer.

【推荐2】Some people believe that humans could live on the planet Mars by the year 2100. Our own planet, the Earth, is becoming more and more c    1     and polluted because of the increase in population. It is hoped that people could start to b    2     a better world on Mars. Here is what life there could be like.

At present, our spaceship are too slow to carry large numbers of passengers to Mars-it would take months, with the development of t    3    , by the year 2100, the journey might only take about 20 minutes in spaceship that travel at the speed of light! However, the spaceship would travel so fast that the journey to Mars might be quite uncomfortable. Many people would f    4     ill.

Humans cannot survive (活下来) without water, oxygen or f    5    . So far, nobody knows whether there would be enough water or oxygen on Mars for people there. Moreover, scientists are not sure whether plants could g    6     on Mars. Food would most probably be in the form of pills (药丸) and would not be so tasty.

Gravity(重力) could be a    7     problem. The gravity on Mars is only about three-eighths of that on the Earth. People would have to wear boots that are specially designed(设计) to stop themselves from floating(飘) off into space.

C    8     with life on the Earth, life on Mars would be better in some ways. People would have more space. They might live in houses with huge comfortable rooms. What’s m    9    , robots would do most of their work so that they could have more time to relax. There would probably be no schools on Mars. Every student would have a computer at home connected to an interplanetary network, they would study at online schools with “e-teachers”.

Life on Mars would be i    10     as well as challenging(有挑战性的).