如图所示的电路，当开关S断开时，电流表的示数是1A ，开关闭合时，电流表的示数将
A．不变
B．增加到2A
C．减少到1/2A
D．增加到4A
答案：A
三联拉压尖段宽度和高度约（）mm，过大或过小都不能被拉拔板牙所夹持。
A.21～25
B.20～24
C.20～35
D.30～35
Not all the students follow the rules. Which of the following statement has the same meaning？
A．None of the students follow the rules.
B．All the students don’t follow the rules.
C．No students follow the rules
D．All of the above
