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问题 单项选择题

代谢活化是指（）。

A.经过生物转化使毒物的毒性增强，甚至产生致癌、致畸、致突变效应

B.Ⅰ相反应可以增毒，Ⅱ相反应可以减毒

C.减毒和增毒必须经过四种反应

D.经结合反应后，水溶性增大，毒性也增大

E.MFO具有两重性

答案

参考答案：A

单项选择题

The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, (51) this is largely because, unlike animals, we stand upright. This means that our noses are (52) to perceiving those smells which float through the air, missing the majority of smells which stick to surfaces. In fact, (53) , we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of (54) human smells when these are diluted to far below one part in one million.

Strangely, some people find that they can smell one type of flower but not another, (55) others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate (56) smell receptors in the nose. These receptors are the cells which sense smells and send (57) to the brain. However, it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when (58) to it often enough.

The explanation for insensitivity to smell seems to be that the brain finds it (59) to keep all smell receptors working all the time but can (60) new receptors if necessary.

51().

A.although 

B.as 

C.but 

D.while
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单项选择题

假设已经生成了名为TESTMENU的菜单，执行该菜单可在命令窗口中输入( )。

A．DO TESTMENU

B．DO TESTMENU.MPR

C．DO TESTMENU.PJX

D．DO TESTMENU.MNX
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