机械密封是通过动环、静环两个端面紧密贴合形成（）而达到密封目的的。
A.磨损
B.摩擦副
C.同步运行
D.液膜
参考答案：B
____in the leg made it impossible for him to walk home.
A．Injured
B．Being injured
C．To be injured
D．Having injured
本质部脊
