精细修剪可用（）。
A.最大剪刀
B.大剪刀
C.中型剪刀
D.小型剪刀
参考答案：B
“Drive-ins” have large parking lots _______ customers are served in their cars by waitresses．
A．who
B．when
C．which
D．where
以下哪个是PCF下的帧间间隔（）
A.SIFS
B.PFIS
C.DIFS
