问题 单项选择题 B型题

又名胆骨化醇()

A.维生素D3

B.维生素B2

C.维生素K3

D.维生素B6

E.维生素A

答案

参考答案:A

解析:维生素D又名胆骨化醇;维生素B熔点为278~282℃,比旋度为-120°~-140°;维生素K其结构为甲萘琨的磺酸钠盐;维生素B是三个结构类似的化合物,即吡多醇、吡多醛、吡多胺,三者在体内可以互相转化,由于最早分离出来的是吡多醇,故一般以它作为维生素B的代表。

单项选择题 A3型题
单项选择题

Today more and more people go to websites when looking for information. Although most readers go to websites for news and e-mail, a form of person-to-person news, or in the form of chatting, they also read books on the web. It’s called electronic book (e-book).

Electronic books could revolutionize reading, but people ought to consider their far-reaching impacts as well. "The e-book promises to cause a slow tragedy on life as we know it," Jason Ohler, professor of technology assessment, university of Alaska Southeast In Juneau, warned the World Future Society, Bethesda, Md. His assessment weighed the pros and cons (赞成和反对的理由) of e-book technology’s impact on social relationships, the environment, the economy, etc. Before you curl up (蜷曲) with an e-book, consider the disadvantages.

They increase eyestrain due to poor screen resolution, replace a relatively cheap commodity with a more expensive one, and displace workers in print-book production and traditional publishing. E-books make it easy to share data, thereby threatening copyright agreements and reducing compensation (补偿) of authors, as well as creating nonbiodegradable (不可生物降解) trash.

On the other hand, e-books save paper and trees, reduce the burden of the carrying and storing of printed books, promote self-sufficiency in learning, and make reading a collaborative experience online. They also create new jobs for writers and artists and encourage self-publishing. In final analysis, Ohler points out, e-books should gain society’s approval if a few conditions are met: make them biodegradable and recyclable, solve the problem of eye fatigue, be sure the "have-nots" get the technology, and support e-book training in schools and business.

In what sense do e-books exert a negative impact on the environment().

A. They are unable to be broken down into harmless products.

B. They consume a lot of natural resources.

C. They produce harmful gases.

D. They are capable of being reused.