下面这篇短文节选自科幻小说The Space Invaders（太空入侵者），阅读这篇短文按照要求回答短文后面的问题：

I am Omega

　　Varon pushed his way through the thick, wet grass of the swamp. Behind him, he heard the sound of loud voices. He tried to go faster, but the thick grass held him back. He had to push his way through it step by step. Varon had come about three kilometres from the Zeron strongroom(保险库) and was very tired.

　　The first part of Varon's plan had beer successful. He had got into the strongroom deep under the ground－he had found the crystal(水晶)－and he had got out again. He had succeeded in stealing one of the most valuable crystals in the Universe. And no one had seen him.

　　But the second part of his plan had gone completely wrong. The guards on the planet Zeron had found his spaceship. Varon had been told that only the strongroom on Zeron was guarded. But now he knew that was wrong. There were guards all over the planet. The guards had been waiting for him when he got back to the spaceship. And now they were chasing(追赶) him and there was no way he could escape.

　　Varon pulled himself slowly to his feet. His face, hands and overalls(防护服)were covered in thick green mud. Varon wiped his hands on his overalls and felt in his pocket. The small, square box was still there. And in the box, there was the Zeron crystal. The crystal would make him rich－very, very rich. But first, he had to get back inside his ship. There was no other way he could escape from Zeron.

　　He now moved out of the long, thick grass. He was standing on harder, drier ground. There were some thick bushes in front of him. Behind him, there was the swamp and the guards who were chasing him. Varon hurried towards the thick bushes.

　　“I must get back to the spaceship.” Varon thought. “I'll have to find some way of tricking the guards. I can't escape from Zeron if I can't get back to the spaceship.”

　　Varon took two steps forward into the bushes. Suddenly he stopped. He knew he was not alone. He dropped down on one knee. There was somebody near him. His hand reached for the laser gun on his belt.

　　“Do not touch your weapon(武器).” said a soft voice.

　　The voice spoke from behind a bush. Varon turned towards the voice and pulled his gun from his belt. He pointed the laser gun at the bush and pressed the trigger(扳机). Nothing happened. Varon pressed the trigger again. Again, nothing happened.

　　The quiet voice spoke once more. “Your gun cannot be used. Put it back in your belt. You will not be harmed.”

　　Varon lowered his hand, but did not put the gun back in his belt. He rose slowly and took a step towards the bush.

　　“You are not permitted to move any nearer,” said the soft, quiet voice. It was a strange voice －neither friendly nor unfriendly.

　　Varon raised his foot to take another step towards the bush. But he could not move his leg forward. He tried and tried to move his leg, but it would not move. He could move backwards, but he could not go nearer the bush.

　　“Who are you?” Varon asked. “What do you want from me?” “I want to help you, Stefan Varon,” said the voice. “You know my name!” said Varon in surprise. No one on Zeron knew him. “Yes, I know your name. And I know what you do. And where you come from. And why you are here. I know every thing. I am Omega.”

　　The leaves of the bush were moved slowly to one side. A tall figure stood in front of Varon. The figure was made of metal. Its face was neither friendly nor unfriendly. It did not have a nose, mouth, eyes and ears like a human. It was a robot!

　　Varon was very surprised. He knew that the guards on Zeron did not use robots. He knew there were no robots on Zeron. Or was he wrong again? A robot was standing here in front of him. “What do you want from me?” Varon asked once again.

　　The robot did not reply. It seemed to be listening to something. Its head moved round to the right. Varon heard the voices of the Zeron guards.

　　“He's over there,” a voice shouted. “Near those bushes!” Varon turned to the left and began to run. Omega raised one arm and pointed it at Varon. A bright, red light came from the metal arm and covered Varon's body. The red light quickly fade

D．When the Zeron guards reached the bushes, they found nothing. Varon and Omega had disappeared.

Answer the following questions.

1．What had Varon stolen?

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2．Why could Varon not get back into his spaceship?

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3．A tall figure stood in front of Varon.

(a) What was the tall figure?

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(b) What was its name?

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(c) Why was Varon surprised?

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4．When the Zeron guards reached the bushes, they found nothing. What had happened to Varon?

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Here's a new warning from health experts: Sitting is deadly. Scientists are increasingly warning that sitting for prolonged periods — even if you also exercise regularly — could be   1  for your health. And it doesn't matter where the sitting takes place — at the office, at school, in the car or before a computer or TV — just the overall number of hours it   2   .

Research is preliminary, but several studies   3  people who spend most of their days sitting are more likely to be fat, have a heart attack or even die.

In an editorial   4  this week in the British Journal of Sports Medicine, Elin Ekblom-Bak of the Swedish School of Sport and Health Sciences suggested that authorities rethink how they define   5  activity to highlight the dangers of sitting.

While health officials have issued guidelines   6  minimum amounts of physical activity, they haven't suggested people try to limit how much time they spend in a seated   7  .

"After four hours of sitting, the body starts to send   8  signals," Ekblom-Bak said. She explained that genes regulating the amount of glucoseand fat in the   9  start to shut down.

Even for people who   10   , spending long stretches of time sitting at a desk is still harmful. Tim Armstrong, a physical activity expert at the World Health Organization, said people who exercise every day —   11  still spend a lot of time sitting — might get more benefit if that exercise were spread across the day,    12  in a single bout.

That wasn't   13  news for Aytekin Can, 31, who works at a London financial company, and spends most of his days sitting    14   a computer. Several evenings a week, Can also teaches jiu jitsu, a Japanese martial art  15  wrestling, and also does Thai boxing.

"I'm sure there are some detrimental   16  of staying still for too long, but I hope that being   17  when I can helps," he said. "I wouldn't want to think the sitting could be   18  dangerous."

Still, in a study published last year that tracked more than 17,000 Canadians for about a dozen years, researchers found people who sat   19  had a higher death risk, independently of whether or not they exercised.

Figures from a US survey in 2003-2004 found Americans spend more than half their time sitting, from working at their desks to sitting in cars.

Experts said more research is needed to    20  just how much sitting is dangerous, and what might be possible to offset those effects.

(   ) 1. A. bad                    B. good               C. mean               D. dead

(   ) 2. A. does                  B. occurs              C. matches            D. dies

(   ) 3. A. advise               B. talk                  C. suggest             D. say

(   ) 4. A. thrown                      B. caught              C. seen                 D. published

(   ) 5. A. biological           B. physical            C. psychological    D. logical

(   ) 6. A. commending      B. mending           C. recommending D. communicating

(   ) 7. A. stand                 B. state                 C. post                 D. position

(   ) 8. A. harmful             B. careful             C. wonderful        D. skillful

(   ) 9. A. head                  B. arm                  C. body               D. foot

(   ) 10. A. sleep               B. rest                  C. walk               D. exercise

(   ) 11. A. and                  B. so                    C. but                   D. then

(   ) 12. A. rather than               B. other than        C. more than        D. less than

(   ) 13. A. bad                  B. harmful            C. disadvantage     D. welcome

(   ) 14. A. behind             B. back                 C. in front of               D. forward

(   ) 15. A. referring          B. involving          C. taking              D. bringing

(   ) 16. A. effects              B. prefects            C. affects              D. offers

(   ) 17. A. inactive            B. active                   C. interactive               D. positive

(   ) 18. A. such                 B. little                 C. lot                   D. that

(   ) 19. A. less                  B. fewer                      C. more               D. further

(   ) 20. A. leave out          B. bring out          C. hold out           D. figure out