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问题 单项选择题

肝癌的影像表现错误的是（）

A.肿瘤以膨胀性生长为主的病灶增长较慢，形成假包膜，可出现晕圈征

B.肿瘤呈浸润性生长一般无包膜形成，边界模糊不清

C.肝癌结节中可形成坏死或偶见脂肪成分

D.肝癌增强扫描静脉期，平扫呈低密度的病灶区CT值迅速升高并明显高于正常肝实质

E.肝癌75％～80％血液由肝动脉供应

答案

参考答案：D

解析：肝癌增强扫描动脉期，平扫呈低密度的病灶区CT值迅速升高并明显高于正常肝实质。

解答题

肤色正常的甲夫妇生下了一个患白化病的孩子；肤色正常的乙夫妇生下两个孩子肤色均正常，由于老大经常在外面玩耍，肤色要比老二黑．请分析：

（1）正常的夫妇生下一个患病的孩子，这孩子的变异是由______决定的，这种变异属于______．（填“可遗传的变异”或“不可遗传的变异”）

（2）乙夫妇的两个孩子肤色的不同是由于______引起的，______并没有发生变化，这种变异属于______．（填“可遗传的变异”或“不可遗传的变异”）
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问答题

Many people are concerned about the economic condition of developing countries — countries whose average per capita GNP is a fraction of that in more industrialized countries. However, for the developing countries, there exist many obstacles to their economic development.
One major obstacle to economic development is population growth. (46) The populations of most developing countries grow at a rate much faster than those of industrialized countries, and the population of some of them is so large that there is barely enough fertile land and other resources to support it. Many less developed countries depend extensively on agriculture, adding to the problem. In these countries, an incentive to have many children exists. (47) Most farms are worked by families, and children can work in the fields at an early age because most farmers believe that more children means more workers. In addition, having many children ensures the parents that someone will look after them in their old age.
Another problem for developing countries is increasing average life expectancy—the average remaining lifetime for persons who reach a certain age. Better education, international aid, and emphasis on health-care facilities help people live longer. A high life expectancy coupled with a high crude birthrate makes it difficult to increase per capita GNP.
Another obstacle to economic growth is limited natural resources. No country can develop beyond its resource potential. Unproductive land or a harsh climate can limit economic growth. (48) Some countries may be fortunate enough to discover a valuable mineral to finance their economic development, but most focus on agriculture and, as a result, their economic growth is hindered by the shortage of natural resources or energy sources needed for industry.
Still another obstacle to economic development is a lack of appropriate education and technology. Any developing countries do not have a highly literate population or the high level of technical skills needed to build an industrial society. In addition, most do not have money to train engineers and scientists. (49) Many developing countries cannot even afford to provide free public education for school-age children, and in those that can, not every child is able to take advantage of it because most of them have to work to help feed their families. As a result, much of the population may not have the basic skills needed to continue with higher education when it is offered.
Government also can be an obstacle to economic development. A country whose government often changes will have a hard time developing economically. Such constant changes impede long-term planning. (50) Economic development is made even more difficult if the political changes occur through violent revolution where industrial facilities may be destroyed.
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