Impressive and complex as it may appear, the rocket, which was 【C4】______ in China over 800 years ago, is a relatively simple device. Fuel that is 【C5】______ in the rocket engine changes 【C6】______ gas. The hot and rapidly 【C7】______ gas must escape, but it can do so only through an opening that 【C8】______ backward. As the gas is 【C9】______ with great force, it 【C10】______ the rocket in the 【C11】______ direction. Like the kick of a gun 【C12】______ it is fired, it 【C13】______ the laws of nature 【C14】______ by Sir Isaac Newton when he discovered that" 【C15】______ every action, there is an equal and opposite reaction."
【C1】______
A. shown
B. been
C. appeared
D. proved
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Oil spills have occurred______.
A. at the site of extraction
B. during transportation
C. before making use of it
D. A＆B
It can be inferred from the last paragraph that scientists______.
A. lack sufficient means to combat lead pollution
B. still consider lead pollution a problem
C. believe lead pollution is not a problem any more
D. have found way to solve the problem of lead pollution
Scientists have started to do the research to______.
A. reveal the reactions of marine organisms to oil
B. find out a way of solving it
C. make a clean of oil spills
D. reveal the life of marine organisms
What is the real cause of the new protectionism？
A. The old one has begun to be unable to explain the new situation of different countries.
B. The welfare developed really fast in Northern Europe.
C. There is some suspect of the regulating ability of the current market.
D. The old protectionism is too limited in its definition.
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