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问题 单项选择题

自抗体中提取纯化IgG应采用下列哪种方法（）。

A.硫酸铵沉淀法

B.亚硫酸钠法

C.离子交换层析法

D.免疫双扩散

E.免疫单扩散

答案

参考答案：C

解析：抗体经过初步纯化后，常采用离子交换层析或亲和层析技术来提取纯化IgG。

单项选择题

There has been much speculation about the origin of baseball. In 1907 a special commission decided that the modern game was invented by Abner Doubleday in 1839. One hundred years later the National Baseball Museum was opened to honor Doubleday. Historians, however, disagree about the origin of baseball. Some say that baseball comes from bat-and-ball games of ancient times. It is a matter of record that in the 1700s English boys played a game they called "baseball". Americans have played a kind of baseball since about 1800. At first the American game had different rules and different names in various parts of the country — "town ball", "rounders", or "one old cat". Youngsters today still play some of these simplified forms of the game.Baseball did not receive a standard set of rules until 1845, when Alexander Cartwright organized the Knickerbocker Baseball Club of New York City. The rules Cartwright set up for his nine-player team were widely adopted by other clubs and formed the basis of modern baseball. The game was played on a "diamond" infield with the bases 90 feet apart. The first team to score 21 runs was declared the winner. By 1858 the National Association of Baseball Players was formed with 25 amateur teams. The Cincinnati Red Stockings began to pay players in 1869.

Which of the following is true about the origins of baseball

A．Historians agree that baseball was invented by Abner Doubleday.

B．Baseball, as played in the early 19th century, differed very little from today’s game.

C．As early as the 1700s, English boys played a game called "baseball".

D．The first standard set of baseball rules was established at the turn of the century.
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单项选择题

人工操纵对车辆施行制动作用的装置叫（）。

A.制动装置

B.手制动机

C.空气制动机

D.基础制动装置
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