可控硅是可控整流器、逆变换流器、无触点交流开关的主要器件，具有（）、（）、无电火花等优点。
参考答案：调节方便；开断迅速。
The old man has two sons, __________ lives with him, so he has always felt lonely since his wife’s death.
A．both of them
B．both of whom
C．neither of them
D．neither of whom
发生过敏性皮疹怎么处理？
