问题 选择题

下面的抽样方法是简单随机抽样的是[ ]

A.在某年明信片销售活动中,规定每100万张为一个开奖组,通过随机抽取的方式确定号码的后四位为2709的为三等奖

B.某车间包装一种产品,在自动包装的传送带上,每隔30分钟抽一包产品,检验其质量是否合格

C.某学校分别从行政人员、教师、后勤人员中抽取2人、14人、4人了解学校机构改革的意见

D.用抽签法从10件产品中选取3件进行质量检验

答案

答案:D

单项选择题 B1型题
单项选择题

The idea of test-tube babies may make you either delighted at the wonders of modern medicine or irritated while considering the moral, or legal, or technological implications of starting life in a laboratory. But if you’ve ever been pregnant yourself, one thing is certain: You wonder what it’s like to carry a test-tube baby. Are these pregnancies normal Are the babies normal

The earliest answers come from Australia, where a group of medical experts at the Queen Victoria Medical Center in Melbourne have taken a look at the continent’s first nine successful "in vitro" pregnancies. The Australians report that the pregnancies themselves seemed to proceed according to plan, but at birth some unusual trends did show up. Seven of the nine babies turned out to be girls. Six of the nine were delivered by Caesarean section (剖腹产手术). And one baby, a twin, was born with a serious heart defect and a few days later developed life-threatening problems.

What does it all mean Even the doctors don’t know for sure, because the numbers are so small. The proportion of girls to boys is high, but until there are many more test-tube babies no one will know whether that’s something that just happened to be like that or something special that happens when egg meets sperm in a test tube instead of a Fallopian tube (输卵管). The same thing is true of the single heart defect; it usually shows up in only 15 out of 60,000 births in that part of Australia, but the fact that it occurred in one out of nine test-tube babies does not necessarily mean that they are at special risk. One thing the doctors can explain is the high number of Caesareans. Most of the mothers were older, had long histories of fertility problems and in some cases had had surgery on the Fallopian tubes, all of which made them likely candidates for Caesareans anyway.

The Australian researchers report that they are quite encouraged. All the babies are now making normal progress, even the twin with the birth defects.

The Australian experiment of the test-tube babies has the following unusual trends EXCEPT that ().

A. most of the babies are girls

B. most of the babies are delivered by means of surgical operations

C. there is a serious heart disease case

D. the babies do not appear to be normal