下列______作行道树时适宜修剪成圆头形或卵形。
A．杨树
B．银杏
C．旱柳
D．水杉
参考答案：C
－Oh, it’s you, Steve! I ______ you.
－No surprising. I’ve just had my hair cut.
A．don’t recognize
B．haven’t recognized
C．didn’t recognize
D．hadn’t recognized
对DTMF双音频号码的扫描周期是（）
A.8ms
B.16ms
C.96ms
D.200ms
