慢性感染通常指病程在A．3周以上 B．4周以上 C．6周以上 D．2_爱下问搜题

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问题单项选择题

慢性感染通常指病程在

A．3周以上

B．4周以上

C．6周以上

D．2个月以上

E．3个月以上

答案

参考答案：D

填空题

选择方框中适当的单词填空。

surprised, millions, easier, history, whole, difficult, popular, working, expensive, different

     We are all busy talking about and using the Internet, but how many of us know the 1. _______ of the Internet.
     Many people are 2.__________ when they find that the Internet was set up in the 1960s. At that time, computers were large and 3. _______________. Computer networks didn't work well.  If one computer
in the network broken down, then the 4. __________ network stopped. So a new network system had to be set up.  It should be good enough to be used by many 5. _______   computers.  If one be sent through
another part.  In this ways, computer network would keep on 6.___________ all the time.
     At first the Internet was only used by the government, but in the early 1970, universities, hospitals and banks were allowed to use it, too. However, computers were still very expensive and the Internet was 7.________ to use. By the start of 1990s, computers software that made" surfing" the Internet 8.___________. Today it is easy to get online and it is said that 9. _______   of people use Internet every day. Sending e-mails is more and more 10._________ among young people.

问答题论述题

均匀剂的作用及其作用机理。