问题 选择题

某校500名学生中,O型血有200人,A型血有125人,B型血有125人,AB型血有50人,为了研究血型与色弱的关系,需从中抽取一个容量为20的样本.按照分层抽样方法抽取样本,则从O型血、A型血、B型血、AB型血的人中分别抽(  )人

A.2,5,5,8

B.2,4,5,8

C.8,5,5,2

D.4,5,5,2

答案

答案:C

因为所以从O型血、A型血、B型血、AB型血的人中分别抽8,5,5,2人.

单项选择题

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

After leaving the Pentagon, MacTaggart could have profited from his connections with defense contractors, but he refused to do so.()

A. After leaving the Pentagon, MacTaggart could have profited from his connections with defense contractors, but he refused to do so.

B. MacTaggart could have profited from his connections with defense contractors after leaving the Pentagon, but he refused to do it.

C. MacTaggart could have profited after leaving the Pentagon from his connections with defense contractors, but he refused to do so.

D. Having left the Pentagon, MacTaggart could have used his connections with defense contractors to profit, but he refused to do it.

E. Refusing to profit from his connections with defense contractors, MacTaggart could have done so after leaving the Pentagon.

单项选择题