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问题 选择题

下列叙述不属于病毒的主要特征的是（ ）

A．由蛋白质和核酸分子构成

B．个体极其微小

C．分裂速度很快

D．专门寄生在活细胞内

答案

答案：C

题目分析：病毒是一种体积非常微小，结构极其简单的生物．没有细胞结构，主要由内部的核酸和外部的蛋白质外壳组成，不能独立生存，只有寄生在活细胞里才能进行生命活动．一旦离开就会变成结晶体．病毒只能利用宿主活细胞内物质合成自身的核酸和蛋白质成分，实现其大量繁殖．

单项选择题

肠扭转最多见于

A．饥饿时运动

B．饱食后卧床

C．饱食后剧烈活动

D．腹部曾有创伤

E．腹内曾手术过
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单项选择题

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.

（15）是（）

A.off

B.up

C.around

D.about
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