指挥人员使用的手势信号均以本人的手心、手指及（）表示吊钩、臂杆和机械位移的运动方向。
A、前额；
B、头部；
C、手臂
参考答案：C
It was his nervousness in the interview ____probably lost him his job.
A．which
B．since
C．that
D．what
氟化钠溶液每日含漱1次的氟浓度应为
A．0．2％
B．O．5％
C．O．1％
D．0．02％
E．0．05％
