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问题 单项选择题 A1/A2型题

甲醛的消毒作用机制为（）

A.抑制某些酶类活性

B.与菌体蛋白的氨基酸结合使之变性

C.抑制生长因子的活性

D.穿透细胞壁使胞浆漏出

E.使细胞内原生质失活

答案

参考答案：B

解析：甲醛的消毒作用机制是使菌体蛋白质变性或凝固。

问答题

　　For years I have been mercilessly lampooned by friends and acquaintances alike for my unorthodox lifestyle choice of having no TV. In an age of increasingly large plasma flat-screens and surround sound, digital home entertainment systems which accost you the minute you walk into someone’s house, people regularly look at me like I’m either severely handicapped or chronically hard done by when I mention that I have no television. I can see the mixture of genuine pity, raw pathos and sheer disbelief in their faces as they stare at me open-mouthed. 　　To be sure, television is a great invention, if handled in moderation. The composite etymological derivation (from the Greek and the Latin words – literally meaning “to see from afar”) tells of a tremendous technological feat which certainly deserves to be applauded. What’s more, if one is discerning, it can be the source of some quality entertainment, instruction and enjoyment. Some of the nature documentaries and arts programmes on BBC 2 are truly fantastic and are well worth the license fee alone. 　　But the sad reality is that young people are rarely discerning and, by dint of poor time management skills, often end up wasting an inordinate amount of precious, never-returning time watching trash, their brains wallowing in a trough of mental lethargy.

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单项选择题

碳素钢按含碳量分为低碳钢、中碳钢和高碳钢，其中中碳钢含碳量一般为（）。

A.<0.25%

B.0.25%~0.6%

C.0.65%~0.70%

D.>0.75%
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