小学生牙周问题主要是
A．龋齿 B．牙龈炎 C．牙周疾病 D．牙列不齐 E．前牙外伤
参考答案：B
If you are able to talk to a friend over the telephone, you feel that you are close ________ the actual
distance is not shortened. [ ]
A. even if
B. so long as
C. if
D. as
下面不是网络操作系统的是（）。
A、Windows98
B、WindowsNT
C、Unix
D、Netware
