问题 选择题

在实验室制取蒸馏水时,下列操作不正确的是[ ]

A.在对烧瓶进行加热时,必须垫上石棉网

B.烧瓶中加入硬水的体积约占烧瓶总体积的2/3

C.为防加热时出现暴沸,在烧瓶中加入几粒沸石或碎瓷片

D.为防止液体通过导管直接流到试管里,加热时,不要液体剧烈沸腾

答案

答案:B

单项选择题
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techniques , but he admitted there would be difficulties in meeting his goal .

“ For example , if you run out of ink while printing on paper , you will throw that paper away . But you cannot throw half-completed buildings away if your material gets stuck , ” he said . Although the printed house is not available to visit , there is a chance for people in Shanghai to see items printed in 3D.

The Belgium-based company Materialise NV held a 3D printing exhibition in Shanghai that started in late 2012 and ended in the middle of 2013 . The company is eager to show Asia what is possible with 3D printing .

“ All the pieces shown here are what cannot be made through traditional techniques . A good example of this customization is hearing aids . More than 10 million people already use 3D printed hearing aids, all made according to the size of their ears , ” said Wim Michiels , executive vice-president at Materialise NV .

“ You can produce anything whenever and wherever you like . You don’t need to set up production lines for pieces that only need a limited amount of products . Setting up a production line is a lot of work . It takes a long time and is very expensive for a limited number of pieces , ” said Michiels .

Kim Francois , managing director of Materialise China , said their European and American clients have already taken the next step toward additive manufacturing with small series production such as hearing aids .

小题1:What is mainly talked about in the text ?

A. The development of 3D printing .

B. A 3D printing show in Shanghai .

C. Varieties of items printed in 3D .

D. The company Materialise NV .

小题2:According to Behrokh Khoshnevis , what is the main difficulty in printing buildings ?

A.Time .

B.Technique .

C.Space .

D.Material .小题3:The example of 3D printed hearing aids was mentioned to show that ______________ .

A.these items used to be impossible to make

B.3D printing has a large market share

C.3D hearing aids help people hear better

D.people need different sized hearing aids小题4:According to the text , 3D printing is suitable for ___________ .

A.mass production

B.making small items

C.small series production

D.reducing production costs