氰化物中毒，选用的解毒剂是（）A .二巯基丁二钠 　　 B.亚甲蓝 　　C .氯解磷

实验室制取硝基苯的主要步骤如下：

①配制一定比例的浓硫酸与浓硝酸的混合液，加入反应器。

②向室温下的混合酸中逐滴加入一定量的苯，充分振荡，混合均匀。

③在50～60℃下发生反应，直到反应结束。

④除去混合酸后，粗产品依次用蒸馏水和5%的NaOH溶液洗涤，最后再用蒸馏水洗涤。

⑤将用无水CaCl₂干燥后的粗硝基苯进行蒸馏得到纯硝基苯。

填写下列空白：

（1）配制一定比例的浓硫酸和浓硝酸混合酸时，操作注意事项是__________________________________________________。

（2）步骤③中，为了使反应在50～60℃下进行，常用的方法是________。

（3）步骤④中洗涤、分离粗硝基苯应使用的仪器是______________________________。

（4）步骤④中粗产品用5%NaOH溶液洗涤的目的是_________________________。

（5）纯硝基苯是无色、密度比水________（填“大”或“小”），具有________气味的油状液体。

经营租赁进口货物一般不复运出境。

In the United States, older people rarely live with their adult children. But in many other cultures children are expected to care (1) their aged parents. In some parts of Italy, the percentage of adult children who (2) with their parents (3) 65 to 70 percent. In Thailand, too, children are expected to take care of their elderly parents; few Thai elderly live (4) . What explains these differences in living arrangements (5) cultures Modernization theory (6) the extended family household to low levels of economic development. In traditional societies, the elderly live with their children in large extended family units for economic reasons. But with modernization, children move to urban areas, leaving old people (7) in (8) rural areas. Yet modernization theory cannot explain why extended family households were never common in the United States or England, or why families in Italy, which is fully modernized, (9) a p tradition of intergenerational living. Clearly, economic development alone cannot explain (10) living arrangements. Another theory associated intergenerational living arrangements with inheritance patterns. In some cultures, the stem family pattern of inheritance (11) . (12) this system, parents live with a married child, usually the oldest son, who then (13) their property when they die. The stem family system was once common in Japan, but changes in inheritance laws, (14) broader social changes brought (15) by industrialization and urbanization, have (16) the (17) .In 1960 about 80 percent of Japanese over 65 lived with their children; by 1990 only 60 percent did-a figure that is still high (18) U.S. standards, but which has been (19) steadily. In Korea, too, traditional living arrangements are (20) : the percentage of aged Koreans who live with a son declined from 77 percent in 1984 to 50 percent just 10 years later. Although most elderly Koreans still expect to live with a son, their adult children do not expect to live with their children when they grow old.

（20）是（）

A.receding

B.removing

C.invading

D.eroding

在一级废水处理系统中，最主要的处理工艺是( )。

A．沉淀

B．离心

C．絮凝

D．中和