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简述静水压力处理的方法进行多倍体诱导的特点？

答案

参考答案：

诱导率较高（可达90%~100%）、处理时间短、受精卵损伤小、成活率高，但需要专门的设备——静水压力容器，小批量生产成本较高。商业生产中多制造较大型的静水压力容器，既可保证诱导的质量，又可以批量生产，降低生产成本。目前已经商业化生产多倍体苗种的企业多数采用静水压力容器处理的诱导方法。

单项选择题

In one sense, we can trace all the problems of the American city back (91) a single starting point: we Americans don’t like our cities very much.
That is, on the (92) of it, absurd. After all, more than three-fourths of us now live in cities, and more are (93) to them every year. We are told that the problems of our cities are (94) more attention in Washington, and scholarship has discovered a whole new (95) in urban studies.
(96) , it is historically true: in the American psychology, the city has been a basically suspect institution, (97) with the corruption of Europe, totally lacking that sense of spaciousness and innocence of the (98) and the rural landscape.
I don’t pretend to be a scholar on the history of the city in American life. But my thirteen years in public (99) , first as an officer of the U. S. Department of Justice, then as Congressman, and now as Mayor of the biggest city in America have taught me (100) too well the fact that a p antiurban attitude (101) consistently through the mainstream of American thinking. Much of the (102) behind the settlement of America was in reaction (103) the conditions in European industrial centers and much of the theory (104) the basis of freedom in America was linked directly to the availability of land and the perfectibility of man outside the corrupt influences of the city.
What has this to do with the predicament of the modern city I think it has (105) to do with it. For the fact is that the United States (106) the federal government, which has historically established our national priorities, has simply never thought that the American city was "worthy" of (107) —at least not to the (108) of expending any basic resources on it.
Antipathy to the city predates the American experience. When industrialization (109) the European working man into the major cities of the continent, books and pamphlets appeared (110) the city as a source of crime, corruption, filth, disease, vice, licentiousness, subversion, and high prices.

A．crowded

B．filled

C．full

D．abundant
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单项选择题

用于对舱壁进行支撑加强的支柱应具有足够强度，其横截面的应不少于（）

A.50mm×50mm

B.80mm×80mm

C.100mm×100mm

D.120mm×120mm
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