A
The earth is the only planet that scientists think has life. Why does the earth have life while the other planets don’t? For one thing, the earth is just the right temperature. As the third planet from the sun, the earth seems to be just the right distance away. The planets which are closer to the sun are so hot. The farthest planets are cold balls.
When the earth developed—which scientists believe may have happened about 4 billion years ago—many gases covered the earth. The gases caused the earth to be hot. But something wonderful happened. The temperature was just right for thick clouds to form. It rained very hard for a very long time. This gave the earth its oceans. Water made it possible for plants to grow. The plants created oxygen in the atmosphere. Oxygen is the gas that humans and animals breathe.
Only one other planet in the solar system seems to be something like the earth. That planet is Mars(火星). Mars is smaller than the earth, and it is quite a bit cooler. But it is not too cold for humans. On some days, the temperatures are as low as a winter day in the northern United States. If you wore a special spacesuit, you could walk around on Mars. The most difficulty is that you have to bring your own air to breathe, becaus e the air on Mars is too thin to breathe.
Mars has the largest volcano(火山)in the solar system. It is sixteen miles high. The highest volcano on the earth is five miles high. Scientists believe that Mars was once much better than it is now. Does this mean there could have been living things on Mars? Scientists are not sure, but there has been no sign so far.
1. Which of the following is NOT the reason that the earth has life?
A. The earth is just the right temperature.
B. There is oxygen in the atmosphere of the earth.
C. The volcanoes on the earth are lower than those on Mars.
D. The earth seems to be just the right distance away from the sun.
2. The underlined phrase “the third planet” in the first paragraph refers to_______.
A. the Earth B. the Moon C. the Sun D. the Mars
3. Which of the following about the Mars is NOT true?
A. Th ere could have been living things on Mars.
B. There is no oxygen in the air on Mars.
C. Mars has the largest volcano in the solar system.
D. Mars is smaller and quite a bit cool er than the earth.
4. Which is the first trouble for human to live on Mars?
A. The volcanoes B. The air C. The food D. The temperature
5. Which of the following is probably the best title for the passage?
A. The Earth B. The Moon
C. Mars is Most Like the Earth D. Planets in the Solar System
