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问题 选择题

设NA为阿伏加德罗常数，下列说法正确的是 [ ]

A．电解精炼铜过程中，电路中每通过NA个电子，阳极溶解铜32g

B．11 2 mol/L的NH4Cl溶液中含NH4+数目为2NA

C．5.6g铁粉与硝酸反应失去的电子数一定为0.3NA

D．1 mol C20H42的分子中含有的共价键数目为61NA

答案

答案：D

单项选择题

梁剪切弯曲时，其横截面上（）。

A.只有正应力，无剪应力

B.只有剪应力，无正应力

C.既有正应力，又有剪应力

D.既无正应力，也无剪应力
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单项选择题

The United States is usually given credit for creating and developing the musical comedy as it is known today. The first musical shows were based (1) everyday American life and the (2) development of the form took place in the United States for more than half a century. (3) the early 1970s, (4) , the London theater has (5) the Broadway stage.

The Black Crook, which opened at Niblo’s Garden in New York City on Sept. 12, 1866, is usually (6) as the inspiration for musical comedy. A troupe of French ballet dancers (7) to be stranded in New York without work (8) a fire damaged the theater (9) they had been booked. In order to keep a (10) to them, the theater producer put the dancers into a melodrama written by Charles M. Barres.

The first stage production that was (11) a musical comedy was a show that was (12) from the Prince of Wales Theater to the Gaiety Theater in London in 1892. Staged by George Edwards, the show called In Town featured a chorus line of Gaiety Girls. The (13) year A Gaiety Girl was equally successful, and a (14) of the show played in New York in the same year. When it was (15) in newspapers, it was designated a musical comedy and regarded as a new (16) of entertainment.

It did not take the form long to (17) in the United States. Almost (18) one of the most renowned talents of the American stage went to work on his own musicals. The singer-dancer George M. Cohan staged Little Johnny Jones in 1904. Cohan, (19) own life story was made into the musical George M (1968), also wrote the books, words, and (20) for Forty-five Minutes from Broadway ( 1906 ), The Little Millionaire ( 1911 ), The Song and Dance Man ( 1923 ), and American Born (1925).

17（）

A. catch on

B.catch out

C. catch to

D. catch off
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