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问题 多项选择题

关于制备单向免疫扩散法的标准曲线的描述，正确是()

A．将已知含量标准抗原稀释成不同浓度，分别置于琼脂板上扩散

B．量取沉淀环的直径，要求准确度达0.1mm

C．以纵轴代表抗原浓度

D．以横轴代表沉淀环直径

E．用半对数纸绘制标准曲线

答案

参考答案：A, B, C, D, E

选择题

现将足量的AgCl分别放入下列物质中，AgCl的溶解度由大到小的顺序是

①20mL 0.01mol/L KCl溶液②30mL 0.02mol/L CaCl2溶液③40mL 0.03mol/L HCl溶液④10mL 蒸馏水⑤50mL 0.05mol/L AgNO3溶液

A．①＞②＞③＞④＞⑤

B．④＞①＞③＞②＞⑤

C．⑤＞④＞②＞①＞③

D．④＞③＞⑤＞②＞①
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课文背诵

People have been  1 cycling in Amsterdam for years. It is a good city for cycling because it is flat and therefore is convenient for bikes. There are also plenty of places for bicycle parking and most streets in the city centre have a bicycle path. Today some people cal the “City of Bicycles” because of   2  there.

In the 1960s, a group of cycling fans had an idea. They believed that it would be better for everybody if cars weren’t allowed in the city centre and only bicycles were.

They were hopeful that this would help to save energy,   3  and  4 . The group  5 and placed them in lots of neighborhoods around Amsterdam for people to use. Anyone was allowed to take them and use them for short journeys. Wherever someone finished a journey they would leave the bike there for someone else to use. The problem was that it didn’t work-thieves took all the bicycles within weeks!
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