C

Scientists have not found any signs of life on Mars yet, but they say a robotic vehicle called “Curiosity” is helping them learn a lot about the planet’s history and climate.

Curiosity landed on Mars in August 2012 after travelling through space for more than eight months. It was sent to Mars by scientists from NASA in the United States.

Curiosity is about the size of a car and has six wheels. It also has a robotic arm, cameras, and instruments that allow it to examine things it finds on the surface. Then it sends the information back to the earth.

Curiosity's main task is to find out if anything could live on Mars, either now or in the past. On Nov. 2, NASA scientists held a press conference to discuss what Curiosity had found in its first two months on Mars.

Curiosity has found soil that is similar to the sand formed by volcanoes on the earth. Scientists say that studying the minerals in Martian soil will help them understand what conditions were like on the planet in the past. Curiosity also found smooth stones like the ones found on river beds and seashores on the earth, where their rough edges have been worn down by water. Mars is very cold and dry now, but scientists say the smooth stones tell them that a river used to run through the place where they were found.

Curiosity has been testing the atmosphere around Mars for a type of gas called methane (甲烷), but so far it has not found any. On the earth, most methane is produced by plants or animals. Methane on Mars might indicate that some type of tiny plants or animals lived there.

Curiosity is the fourth robotic vehicle to be sent to Mars. It will continue to explore the planet for about two years.

46. Which of the following descriptions about Curiosity is TRUE?

A．It landed on Mars in January 2012.

B．It is small in size and has four arms.

C．It took over eight months to arrive in Mars.

D．It was sent to Mars by scientists from Russia.

47. According to the information sent back by Curiosity, scientists believe that________．

A．there's no air on Mars

B．Mars is warm and wet now

C．the soil on Mars is rich

D．there used to be water on Mars

48. The underlined word “they” in Paragraph 5 refers to“________”．

A．smooth stones

B．rivers

C．robotic vehicles

D．volcanoes

49. We know from the sixth paragraph that________．

A．some tiny animals once lived on Mars

B．there are no plants or animals on Mars now

C．the atmosphere around Mars is full of methane

D．Curiosity is designed to test the atmosphere around the earth

50. What is the main idea of the passage?

A．Humans benefit a lot by going to Mars.

B．Scientists will stop the research on Mars soon.

C．It is possible to build an earth-like environment on Mars.

D．A robotic vehicle helps scientists get useful information from Mars.
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