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问题 填空题

天体的影锥可分为（）、（）和（）三部分，因各部分所得太阳辐射都少于影区之外，故当月球的影锥扫过地球时，不同影区的观测者将观测到不同类型的（）。

答案

参考答案：本影；半影；伪本影；日食

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.

19（）

A.secure

B.ensure

C.reassure

D.incur
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单项选择题

关于抽样研究，描述不正确的是

A．获取样本时应遵循随机化原则

B．实施抽样时要使总体中每一个体有同等机会被抽到

C．研究者可随意抽取总体中任意部分作为样本，以保证其典型性

D．抽得的样本对总体有代表性，以及更好地对总体进行统计推断

E．严格白勺随机抽样有助于减少样本的偏性
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