1、单选题：
Which of the following is not a commonly used semiconductor material'? （    ） 
选项：
A:carbon
B:lead
C:silicon
D:germanium
答案: 【lead】

2、单选题：
The characteristic of an ideal diode are those of a switch that can conduct current（    ） .
选项：
A:in both directions
B:in one direction only
C:in both directions but in only one direction at a time
D:depends on the circuit it is used in
答案: 【in one direction only】

3、单选题：
When a diode is doped with either a pentavalent or a trivalent impurity its resistance will （    ） .

选项：
A:increase
B:decrease
C:make the resistance stable against variation due to temperature
答案: 【decrease】

4、单选题：
The piecewise linear model, equivalent circuit of the diode consists of （    ）.
选项：
A:a junction capacitor, a battery, a small resistor, and the ideal diode
B:a battery, a small resistor, and the ideal diode
C:a battery and the ideal diode
D:the ideal diode
答案: 【a battery, a small resistor, and the ideal diode】

5、单选题：
When a p-n junction is reverse-biased, its junction resistance is （    ）.
选项：
A:high
B:low
C:determined by the components that are external to the device
D:constantly changing
答案: 【high】