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（1）学校、家庭、办公室常用的净水器的基本原理可用如图所示的简易净水装置表示．其中所用的小卵石、石英沙等的作用是______，起吸附作用的是______；

（2）长期饮用硬水对人体健康不利．要检验日常使用的自来水是不是硬水，可用______，倘若检验得出是硬水，可采用降低水的硬度的方法是______．

答案

（1）其中所用的小卵石、石英沙等的作用是过滤，起吸附作用的是活性炭．故填：过滤；活性炭．

（2）向水中进入肥皂水时，如果产生的泡沫较多，是软水；如果产生的泡沫很少，是硬水．故填：肥皂水．

加热煮沸时，水中的钙离子和镁离子能够以沉淀的形式从水中析出，蒸馏能够得到几乎纯净的水．故填：煮沸或蒸馏．

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Americans have four primary avenues for making friends: at work, at school, through a hobby or a (1) such as volunteer work and discussion group, or through a family or (2) .
In American culture, a job is more than the work that one performs between the hours of 9 a.m. and (3) . Work becomes a major socializing influence. Many young mothers who (4) their jobs to care for small children remark on the loneliness of their new lifestyles because they have lost their forum for (5) .
A great number of American employers recognize business social (6) and use it to build a family atmosphere on the job so that employees will feel (7) in their work environment. Some employers arrange company get-togethers in their home or at a (8) . American companies have at least one (9) annually, usually at Christmas time. Many corporations have (10) where employees and administrators alike dress (11) to play games such as baseball and volleyball.
Top American administrators often hold social gatherings (12) . Depending upon the size of the employer’s home and the number of (13) . These social gatherings may be picnics, pool parties, or (14) . If the company is large, an employer may hold what Americans call (15) . For an open house, the employer will invite his employees to come to his home (16) between 1 p.m. on a certain day. Those invited usually stay for (17) , chatting with the other guests and their host. People come and go (18) during the designated hours, and the host keeps refreshments, usually (19) or hors d’oeuvres and beverages, available for all who come. For such social gatherings, it is considered (20) the invitation unless you have an excellent reason.
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单项选择题

雕版印刷术在北宋时发展迅速，广泛应用于刻印书籍。国子监刻印的书，后世称为( )；政府机构刻印的书，统称为( )；民间书坊刻印的书称为( )。

A．监本、官本、民本

B．监本、正本、次本

C．监本、正本、副本

D．监本、官刻本、坊刻本
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