题目内容
A number of persons have expressed concern about possible health dangers to workers who use devices called video-display terminals (终端) or VDTs. These are the devices used to show computer information. Some reports link VDTs to health disorders including eye problems and muscle problems. Even the health of the pregnant women and their unborn babies is said to be endangered. Video-display terminals produce low levels of the electromagnetic radiation(电磁辐射). Experts say most modern VDTs have been designed to limit the dangers from such radiation. However, study shows that even low levels of electromagnetic radiations can affect the growth of the cells. As a result, some doctors advise women to stop working with VDTs while they are pregnant. One study found women who work with VDTs in early pregnancy are more likely than others to have their pregnancy end unexpectedly. Researchers said that this does not necessarily mean that VDTs themselves cause problems. Some experts said the findings show working conditions, not the machines, cause the problems. Law makers in m6re than American states have proposed bills to control working conditions for VDT operators.
What kind of disease does the VDTs cause？
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There are many reasons of the tidal action which is a very complicated phenomenon involving many factors all of which must be considered to predict tide in any one place at any one time. The alternate rise and fall of the surface of the seas and the ocean is mainly caused by the attractive force of the moon alone. When the attraction is great, the tide is high; and conversely when the attraction is minimal, the tide is low. Between the high and the low tide is a period of a little over six hours, being called during its rise a flood tide, and during its fall an ebb tide.
The sun also exerts its effect on the tide, being a lit fie less than half as much as the moon, although its mass is so much greater. When the moon and the sun are horizontal, the highest high tide occurs and when they are vertical the lowest low tide takes place.
The wind also plays an important part in the modification of the normal rise and fall of the tide. Thus these factors affect each other, either detracting or adding to the attractive forces to add or subtract from the weight of the tide. But the tides still move inexorably on, rising twice a day, getting a little later each day and posing a problem of correctly predicting their heights and lows.
Which of the following factors will not affect the time of the tide？
She went round the room, talking to each woman in turn but ______ little response from any
It' s bad policy for developing countries to sacrifice environmental protection to ______
会计的对象是指会计所核算和监督的内容,包括企业生产经营过程的全部内容。()
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