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问题 单项选择题 A1型题

乳牙容易患龋的因素是（）。

A.乳牙解剖形态

B.乳牙钙化度低、抗酸力弱

C.食用软质、粘稠、含糖量高的食物

D.口腔自洁和清洁作用差

E.以上都是

答案

参考答案：E

单项选择题

向用人单位提供可能产生职业病危害的设备的，应当提供中文说明书，并在设备的醒目位置设置（）。

A、警示标识

B、中文警示说明

C、警示标识和中文警示说明
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填空题

Part 1


·Read the following passages, eight sentences have been removed from the article.
·Choose from the sentences A-H the one which fits each gap.
·For each gap (1-8) mark one letter (A-H) on the Answer Sheet.
Buzz Aldrin, the second man to walk on the Moon, is a long-time fan of space tourism. Aldrin climbed out of Apollo11 hot on the heels of Neil Armp in 1969. (1)
Together with scientists from Purdue University, the Massachusetts Institute of Technology, and the University of Texas, Aldrin is designing spacecrafts that would perpetually cruise between Earth and Mars. (2) "Some day, people will go to Mars on a regular basis," says team member James Longuski, a professor at Purdue. (3)
The average distance between Mars and Earth is 48 million miles. (4)
It sounds like a trip that would require a lot of fuel. According to the engineers, the cyclers may have a natural, renewable "fuel" supply: from the gravitational forces of the Sun, the planets, and their moons.
As a spacecraft travels close to a planet, its flight path is bent, causing it to whip around the planet and significantly increasing its speed (it’s as if the planet’s gravity gives the passing spacecraft a kick into space). (5) It’s not just science fiction: it might help us get Mars with very little fuel on board, in a journey that would take as little as six to eight months.
"The cycler is essentially in orbit around the Sun and makes regular flybys of Earth and Mars," says James Longuski. "Once you put your vehicle into a cycler orbit, it continues on its own momentum, going back and forth between Earth and Mars. (6)
When the cycler flies by Earth, it will be traveling at a speed of about 13,000 miles per hour.
(7) This is sort of like a bus that doesn’t stop," Longuski says. "When it comes by, you have to run alongside of it and grab on."
AIdrin and his group think that the first cycler could be on its way by as soon as 2018. (8) (It seems a long way off now, but it’s closer than you think!)
Fasten your seatbelts and make sure your seatback is in its upright position. Your flight to space may be departing soon.
  • A. These crafts, known as "cyclers", would ferry people and supplies between the two planets, enabling humans to colonize Mars — something that has long been dreamed about in science fiction.
  • B. Most people are convinced that we are going to do this; the only question is when.
  • C. So, if you’re in middle school now, you could be taking a trip to Mars by the time you’re in your thirties.
  • D. To get a sense of just how far this is, try doing this calculation: Given that there are 2,500 miles between New York and Los Angeles, how many times would you have to travel from NY to LA and back to cover the same distance’
  • E. Now, at the age of 72, Aldrin is working on a new project that could put more of his fellow humans in space — namely, on journeys to one of our most fascinating neighbors, Mars.
  • F. This is the "slingshot" trajectory that you may have seen in movies.
  • G. Space taxis will be needed to bring people from the surface of the planet to intercept the cycler.
  • H. You may need to carry some propellant for an occasional boost, but it’s pretty much a free trip after that.
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