下列化合物中既有离子键又有共价键的是( )
A.KBr
B.NH4Cl
C.HF
D.O3
答案:B
— Why was Fred forced to leave school?
— Because he was _____ of cheating in the English exam.
A.blamed
B.accused
C.charged
D.caught
网桥是一种在多个使用相同的通信协议的网络段之间传输信息的设备。