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  After spending years searching for a planet with life, scientists may have found one.In September 2010, a team of US scientists discovered an Earth-sized planet called Gliese 581 g.It has a surface temperature neither too hot nor too cold for liquid(液态)water.Scientists think there is a chance that the planet could have life.

  The planet Gliese 581 g goes around a star called Gliese 581, which is about 20 light-years from Earth.That is about 194 trillion(万亿)kilometres-500 million times farther away from us than the moon.

  A spacecraft traveling at a one-tenth of the speed of light would reach Gliese 581g within about 220 years.A human can’t live that long, but robotic explorers could make the job easier.However, our fastest spacecraft don’t come anywhere near that one-tenth light-speed mark.

  At present, scientists don’t know what the surface might be like on Gliese 581 g.What they know is that the planet is at the sight distance from its star to have liquid water.It’s also at the right distance to have an atmosphere that could protect the water if it is on the surface.

  Although spacecraft won’t be getting there anytime soon, one way to look for life on Gliese 581g is to turn our radio telescopes(望远镜)towards the planet and search for radiation(放射).By studying the radiation, scientists would find out about the chemicals(化学物质)around the planet and discover it Gliese 581 g has an atmosphere.If it has one, studying the atmosphere would give us a good idea if the planet has life or not.But it’ll probably be many years before we can do this properly.

  People have been arguing about whether there is alien life on Gliese 581 g.Any discussion about alien life is just guessing at this point, according to its discoverers.

(1)

What did scientists find in September 2010?

[  ]

A.

A planet with water.

B.

A planet similar to the earth.

C.

A planet without life.

D.

A planet near the earth.

(2)

According to the article, Gliese 581 g _________.

[  ]

A.

is at the right distance from its star

B.

moves around the earth

C.

is as far away from us as the moon

D.

can be reached in about 220 years

(3)

Paragraph 5 is mainly about _________.

[  ]

A.

the possibility of living on Gliese 581 g

B.

the kinds of chemicals around Gliese 581 g

C.

the way of looking for life on Gliese 581 g

D.

the aim of studying the radiation on Gliese 581 g

(4)

Which of the following is the best title for the passage above?

[  ]

A.

Gliese 581 g, a Likely Living Planet

B.

Gliese 581 g, a Likely Living Planet

C.

Gliese 581 g and Its Star

D.

Gliese 581 g and Radiation

  The Indians invented and developed the system of numbers from 1 to 9 and 0. We can use the ten numbers to make any number from the biggest to the smallest.

  However, the ancient Romans invented a different system (系统) of numbers. They used symbols (符号) and replaced them. 1 is “Ⅰ” and 2 is “Ⅱ”. For larger numbers, they invented new symbols—5 is “Ⅴ”, 10 is “Ⅹ”, and so on. But they didn’t have a symbol for zero.

  Here’s a table of the Roman numbers.

1

5

10

50

100

500

1,000

L

C

D

M

  The Romans combined their symbols. In this way, “Ⅶ” means “5+1+1”, or 7. However, they found that “ⅡⅡ” (for 4) and “ⅤⅡⅡ” (for 9) were too confusing, so they thought out another idea.

  If the “Ⅰ” comes after the “Ⅴ”, then you add it (Ⅵ is 6); if the “Ⅰ” comes before the “Ⅴ”, then you subtract (减去) it (Ⅳ is 4). The rule is that you are allowed to add up to three (e.g. Ⅷ is 8), but only subtract one (e.g. XL is 40).

  How to remember the symbols?

  Ⅰis like a finger. In a whole hand, the thumb (拇指) and the little finger make a V. Ten fingers are both hands, so the two Vs make an X..

  Here is a way to remember the other symbols (L, C, D, M):Little Cats Drink Milk.

(  ) 51. How many numbers can we make according to the Indians’ system ?

     A. three: 0, 9, 1   B. ten      C. eleven    D. lots of

(  ) 52. Which number was not in the ancient Roman’s number system?

     A. 1       B. 9      C. 0       D. 5

(  ) 53. What does the underlined word “combined” probably mean in the passage?

     A. 合并     B. 分离     C. 增加     D. 削减

(  ) 54. What does MD mean according to the Romans’ rule of calculating?

     A. 500      B. 1000     C. 1500     D. 2000

(  ) 55 Which sentence is NOT true according to the passage?

     A. “Little Cats Drink Milk” can help us to remember some of the numbers symbols.

     B. The Indians invented the system of numbers from 1 to 9 and 0.

     C. You are not allowed to make a number like “XXL”

     D. The ancient Romans repeated symbols to make any number.

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