公共英语二级
A pure virus(病毒) could be kept in a bottle, just like hundreds of other chemicals. Yet,when a virus is placed on a living thing, it comes to rife. As long as it is on a living material, it grows.
A difficult question still remains--what is a virus? Is it living or chemical? Men of science had always thought life and not-rife to be as different as black and white. With the discovery of the vi-rus, they became aware of a grey area that was neither black nor white.
Until the 1930´ s, it was accepted that there was also a great difference in size between the lar-gest chemical molecules (分子) and the smallest living things. As new and much finer filters ( 过滤器) were invented, men were able to measure viruses. The first virus to be measured was found to be about 100 millimicrons(毫微米) across.
The largest known chemical molecule measures only 22 millimicrons. The smallest living thing measures almost seven times that size or 150 millimicrons. When viruses were measured, they were found to range in size from 16 millimicrons to 300 millimicrons. Most were found to be larger than the largest chemical molecules and smaller than the smallest living things.
The answer to the puzzle--what is a virus?--must be that it is both riving and not living. In a living cell, it is a live thing. In a bottle, it is nothing more than a chemical. We now realize that the virus is actually a link between life and not-rife.
What IS this text mainly about?
A．How viruses should be understood．
B．The effect viruses have on living things．
C．How filters are used in studying viruses．
D．The researches scientists do with viruses．
你可能感兴趣的试题
A．A large chemical molecule．
B．A dead chemical．
C．An active virus．
D．A living cell．
A．The discovery of unknown chemicals．
B．Viruses in a state of living and not living．
C．A difficult question unsolved about viruses．
D．The colour of viruses between black and white．
A．Viruses．
B．New filters．
C．Living cells．
D．Chemical molecules．
最新试题
Where does the conversation take place?
What are they talking about?
What are these two people talking about?
假定你是李明，你的外国朋友Bob想过一个特殊的周末，你打算带他去农村一日游。请你用英文给他写封信，内容要点如下： 1．去
What service Can a GBH card offer for a fixed period time?
Which is most useful if you plan to go to shows in London?
One use ofthe London Pass is to __________．
根据下面资料，回答题。 Good Value Britain TRAVELING IN SCOTLAND Scotla
Which of the following is the smallest in size?
What do the underlined words“a grey area”in paragraph 2 ref