用经纬仪检查精密回转工作台的分度误差时,平行光管一般放置在离经纬仪约()处。 A.3

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问题:

用经纬仪检查精密回转工作台的分度误差时,平行光管一般放置在离经纬仪约()处。

A.3m

B.4m

C.5m

D.2m

考点:机修钳工考试机修钳工(技师)机修钳工(技师)题库
题型:单项选择题

以下哪一项是直肠排便功能最重要的环节()。

A.直肠下段发生排便神经反射

B.结肠的蠕动,粪便下行

C.直肠能分泌粘液

D.外括约肌的自主松弛

E.腹压的增加

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设实数x,y满足条件 
x+1≥0 
x-y+1≥0 
x+y-2≤0
则y-4x的最大值是______.
题型:单项选择题

小狗听到主人叫它的名字就能跑过来,这是()的反应。

A.第一信号系统

B.非条件反射

C.第二信号系统

D.第三信号系统

题型:单项选择题

How long you live has a lot to do with your environment and lifestyle, but exceptional(特别的)long life may have even more to do with your genes. For the first time, researchers have discovered a genetic recipe(基因谱)that accurately predicts who may live to 100 and beyond.

Analysis shows that 90% of the participants who lived to 100 had at least one of the signature genetic clusters(标志基因组). Dr. Thomas Perls at the Boston University School of Medicine said, “We realize this is a complex genetic puzzle. There is a long way for us to go to understand how the integration(融合)of these genes—not just with themselves but with environmental factors—is playing a role in this long life puzzle.”

Perls has studied many factors that contribute to long life, and he is the first to acknowledge that living longer isn’t likely to be simply a matter of genes. His previous work has shown, for example, that among most elderly people who live into their 70s and 80s, about 70% can owe their long life to environmental factors such as not smoking; eating a healthy, low-fat, low-calorie diet; and remaining socially engaged and mentally active throughout life.

It seems clear that those who live extremely long are benefiting from a special DNA. In fact, Perls believes that the older a person gets, the more likely it is that his or her genes are contributing to those extended years.

小题1:Which of the following is TRUE according to Paragraph 2?

A.Most long-living people have special long-life-related genes.

B.Ninety percent of the participants lived to 100 years of age.

C.All the long-living people have only one signature genetic cluster.

D.Scientists know how the integration of the genes helps people live long.小题2: Perls may most likely agree that         .

A.most people living extremely long benefit from not smoking

B.living longer just depends on certain genetic recipes

C.environmental factors play an important role in long-living

D.being mentally active has nothing to do with living an old age小题3: Which of the following is FALSE according to the text?

A.Remaining socially engaged helps a person to live long.

B.A genetic recipe can accurately predict who may live to 100 and beyond.

C.Perls is the first to think living longer is just a matter of genes.

D.The older he gets, the more likely the genes contribute to his extended years.小题4:Which of the following would be the best title for the text?

A.Genes May Predict Who Lives to 100

B.Environment And Genes

C.Genes, the Secret of Long Living

D.Lifestyle And Genes

题型:单项选择题

小儿常易与急性阑尾炎混淆的疾病是()。

A.腹型卒中

B.肠系膜淋巴结炎

C.肾胚胎瘤

D.溃疡性结肠炎

E.重复畸形囊肿感染

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