题干

根据下表所做的有关分析,错误的是(  )

溶液

溶质的元 素组成

检测试剂

颜色反应

溶质的基 本单位

甲

C,H,O

①

红黄色

葡萄糖

乙

C,H,O,N等

双缩脲试 剂

②

③

A:甲可能是麦芽糖溶液

B:①是本尼迪特试剂,使用时需沸水浴加热

C:乙可能是一种酶溶液

D:②是紫色,③是核苷酸

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答案(点此获取答案解析)

D

同类题4

    Sunday is more like Monday than it used to be. Places of business that used to keep daytime “business hours” are now open late into the night. And on the Internet, the hour of the day and the day of the week have become irrelevant. A half century ago in the United states, most people experienced strong and precise dividing lines between days of rest and days of work, school time and summer time. Today the dividing lines are still there, but they seem not clear.
    The law in almost all states used to require stores to close on Sunday; in most, it no longer does. It used to keep the schools open in all seasons except summer, in most, it still does. And whether the work week should strengthen its legal(法律的)limits, or whether it should become more changeable, is often debated(争论). How should we, as a society, organize our time? Should we go even further in relaxing the dividing lines of time until we live in a world in which every minute is much like every other?
    These are not easy questions even to ask. Part of the difficulty is that we seldom recognize the “law of time” even when we meet it face to face. We know as children that we have to go to  school a certain number of hours, a certain number of days, a certain number of years – but unless we meet the truant officer(学监), we may well think that we should go to school because of social custom and parents’ requirement rather than to the law. As adults we know “extra pay for overtime working” very well, but less familiar with the fact that what constitutes(构成)“overtime” is a matter of legal thing. When we turn the clock forward to start daylight – saving time, have we ever thought to ourselves: “Here is the law in action”? As we shall see, there is a lot of law that has great influence on how organize and use time: compulsory education law, overtime law, and daylight-saving law – as well as law about Sunday closing, holidays, being late to work, time zones, and so on. Once we begin to look for it, we will have no trouble finding a law of time to examine and assess.