问题 单项选择题

关于草酸钠抗凝剂的叙述,正确的是()

A.可与血液按1:9的比例使用

B.常用浓度为0.5mol/L

C.可与血中钙离子生成可溶性螯合物

D.对Ⅴ因子有保护作用

E.可用于血细胞计数

答案

参考答案:A

解析:草酸盐可与血中钙离子生成草酸钙沉淀,通常用0.1mol/L浓度,与血液按1:9比例使用,过去主要用于凝血象检查。实践发现其对V因子保护功能差,影响凝血酶原时间测定效果,另外由于其成钙结合形成的是沉淀物,影响自动凝血仪的使用,因此认为凝血象检查选用枸橼酸钠为抗凝剂更为适宜。

判断题
阅读理解

It is known to us that computer users are being warned by industry experts to pay attention to secret codes which could be used to record their conversation.

E-mails, screen savers, and electronic greeting cards can carry a secret code which is able to turn on the computer’s microphone, make a recording, and forward it to someone else without the user’s knowledge.

In fact any attachments (附件) sent to a computer, whether it is a game of Space Invaders, or a moving picture, can possibly be used to spy (窥探).

Experts say people should always think twice about opening attachments because --- although not common --- bugging (窃听) by computer can and has been done.

Bill Lyons, head of the Internet Security Company Finjan, said, “People in the army have tested this and you can be sure, if people in general are aware of it, then computer hackers (黑客) are aware of it. The frightening thing is that there are tools on the Internet which people, using a simple search method, can find, and which will enable them to attach this dangerous code to simple attachments.”

小题1:What is the advice given in the passage?

A.Use secret codes to record other people’s conversation.

B.Be careful when opening an attachment.

C.Never open any attachments.

D.Never use secret codes.小题2:What worries the experts is that ___ .

A.nobody seems to believe such things

B.nobody knows the danger of the code

C.tools can easily be used to tie dangerous codes to e-mails

D.effective ways can never be found to deal with the problem.小题3:Which of the following is TRUE according to the passage?

A.A moving picture cannot be used to spy.

B.Electronic greeting cards cannot carry a secret code.

C.A secret code is used to destroy the computer system.

D.Any attachments sent to a computer may carry a secret code.