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问题 单项选择题

在pH、离子强度等条件固定时，蛋白质分子量越大，用以沉淀的PEG浓度

A．越小

B．越大

C．与蛋白质分子量无关

D．与蛋白质分子量相等

E．与蛋白质的浓度相等

答案

参考答案：A

解析： PEG是沉淀反应中经常使用的增浊剂，其作用是消除蛋白质分子周围的电子云和水化层，促进能特异结合的抗原、抗体分子靠近，结合形成大分子复合物。在其他条件固定时，蛋白质分子量越大越容易沉淀，用以沉淀的PEG浓度越小。

多项选择题

下列各项中，影响利润表“所得税费用”项目金额的有( )。

A．当期应交所得税

B．递延所得税收益

C．递延所得税费用

D．代扣代交的个人所得税
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单项选择题

Throughout the 19th century and into the 20th, citizens of the United States maintained a bias against big cities. Most lived on farms and in small towns and believed cities to be centres of (1) , crime, poverty and moral (2) Their distrust was caused, (3) , by a national ideology that (4) farming the greatest occupation and rural living (5) to urban living. This attitude (6) even as the number of urban dwellers increased and cities became an essential (7) of the national landscape. Gradually, economic reality overcame ideology. Thousands (8) the precarious (不稳定的) life on the farm for more secure and better paying jobs in the city. But when these people (9) from the countryside, they carried their fears and suspicions with them. These new urbanities, already convinced that cities were (10) with great problems, eagerly (11) the progressive reforms that promised to bring order out of the (12) of the city.

One of many reforms came (13) the area of public utilities. Water and sewerage systems were usually operated by (14) governments, but the gas and electric networks were privately owned. Reformers feared that the privately owned utility companies would (15) exorbitant (过渡的) rates for these essential services and (16) them only to people who could afford them. Some city and state governments responded by (17) the utility companies, but a number of cities began to supply these services themselves. (18) of these reforms argued that public ownership and regulation would (19) widespread access to these utilities and guarantee a (20) price.

（1）（）

A.eruption

B.corruption

C.interruption

D.provocation
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