牵拉髋和踝屈肌，有利于（）
A.行走摆动
B.穿戴支具
C.站立稳定
D.处理大、小便
E.转移性活动
参考答案：A, C
He had to___ before they finished the course because they were not well disciplined.
A．drop in
B．drop out
C．drop off
D．drop by
浮选三相体系指的是什么？
