压缩波又称为（）。
A、莱姆波
B、切变波
C、纵波
D、横波
参考答案：C
一个C类地址的网段中要划分出32个子网，下面那个子网掩码最适合（）.
A.255.255.255.224
B.255.255.255.240
C.255.255.255.255
D.255.255.255.248
Do you enjoy ______ the piano? [ ]
A. play
B. playing
C. played
D. plays
