1、单选题：
Which of the following is not a commonly used semiconductor material'? （ ）
选项：
A:lead
B:germanium
C:carbon
D:silicon
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 but in only one direction at a time
B:in both directions
C:in one direction only
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:decrease
B:increase
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:the ideal diode
B:a junction capacitor, a battery, a small resistor, and the ideal diode
C:a battery and the ideal diode
D:a battery, a small resistor, and 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:low
B:high
C:constantly changing
D:determined by the components that are external to the device
答案: 【high】