二极管的安全极限参数为______。 A．IF、IR B．UR、IR C．IF、

乳腺囊性增生病的主要处理措施是（）

A.服药

B.手术

C.定期复查

D.激素治疗

E.理疗

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

     Recently some American scientists have given a useful piece of advice to people in industrialized nations,

They say people should eat more of the same kind of food eaten by humans living more than 10,000 years ago.

1_____

     The scientists say that the human life has changed greatly. Our bodies have not been able to deal with these

changes in lifestyle and this had led to new kinds of sicknesses. 2_____ So they are called "disease of

civilization". Many cancers and disease of blood system are examples of such diseases.

     Scientists noted that people in both the Old Stone Age and the New Stone Age enjoyed very little alcohol or

tobacco, probably none. 3_____ However, a change in food is one of the main differences between life in

ancient times and that of today.

     Stone Age people hunted wild animals for their meat, which had much less fat than domestic ones. They

ate a lot of fresh wild vegetables and fruits. They did not have milk or any other dairy products, and they made

very little use of grains. 4_____ We eat six times more salt than our ancestors (祖先). We eat more sugar. We

eat twice as much fat but only one third as much protein and much less vitamin C. 

     5_____ But scientists say that we would be much healthier if we eat much the same way as our ancestors

did, cutting the amount of fatty, salty and sweet food.

A. These new sicknesses were not known in ancient times.

B. People today probably do not want to live the way people thousands of years ago did.

C. Ancient people also lived in large groups.

D. But today, we eat a lot of these.

E. Ancient people also got a great deal of physical exercise.

F. In that case, they would live much healthier.

G. People today probably live the same life as people thousands of years ago did.

冷热水管同时安装应符合（）。

A.上下平行安装时，热水管应在冷水管的下方

B.上下平行安装时，热水管应在冷水管的上方

C.垂直平行安装时，热水管应在冷水管的左侧

D.垂直平行安装时，热水管应在冷水管的右侧

下列关于激光钎焊说法错误的是（）。

A.激光钎焊只对连接部位局部加热

B.加热速度快，冷却速度慢，故接头组织细密、可靠性高

C.非接触接热

左边给定的是纸盒的外表面，下面哪一项能由它折叠而成（）

A.A

B.B

C.C

D.D