调相机在起动前应将励磁电阻调至（）位置。A.中间 B.最大 C.最小 D.任意

甲将闲置不用的工程设备出售给乙，双方约定3天后交付设备，次日，甲又将该设备卖给丙，并向丙交付了该设备。经查，丙不知甲与乙之间有合同关系。关于甲、乙、丙之间的合同效力的说法，正确的是()

A.甲与乙、丙之间的合同均有效

B.甲与乙之间的合同无效，甲与丙之间的合同有效

C.甲与乙、丙之间的合同均无效

D.甲与乙之间的合同先生效后失效，甲与丙之间的合同有效

从某一优点或者缺陷出发去评价应聘者其他方面，这属于( )

A．第一印象

B．对比效应

C．晕轮效应

D．录用压力

除去下列各组物质中含有的杂质，所用试剂和方法均正确的是 

有关混杂因素和混杂偏倚的说法正确的是（）

A.有混杂因素存在一定会产生混杂偏倚

B.混杂因素主要指年龄、性别、职业这些人口学特征因素

C.混杂偏倚引起的继发关联是典型的混杂偏倚类型，而引起的间接关联则不是混杂偏倚

D.在分析阶段控制混杂的方法多采用多元分析，不仅能分析暴露因素的效应也能估计混杂因素的效应

E.暴露因素和混杂因素的概念是绝对的，有些因素只能是暴露因素，而另一些因素一定是混杂因素

Many people are surprised when they find the Internet(因特网)was set up in the 1960s. At that time, computers were large and expensive. Computer networks(网络) didn’t work well. If one computer in the network broke down, then the whole network stopped. So a new network system (系统) had to be set up. It should be good enough to be used by many different computers. If a part of the network was not working, information could be sent through another part. In this way computer network system would keep on working all the time.
At first the Internet was only used by the government, but in the early 1970s,universities(大学) ,hospitals and banks were allowed(允许) to use it too. However, computers were still very expensive and the Internet was difficult to use. By the start of the 1990s, computers became cheaper and easier to use.
Today it is easy to get on-line(上网) and it is said that millions of people use the Internet every day. Sending e-mail is more and more popular among students.
The Internet has now become one of the most important parts of people’s life.

A good network system ______.

A. can keep on working
B. will stop working
C. will break down soon