下列机构中，要求自锁的是（）。
A、摇臂钻床的摇臂升降
B、齿轮机构的从动件
C、螺旋千斤顶
D、水闸闸门的起落
参考答案：C
Some cyclists make the ______ that traffic laws do not ______ them. It is not true, _____.
A．assumption; apply to; though
B．thought; apply to; however
C．assuming; apply for; though
D．idea; apply for; however
由馏分组成即（）可以辨别原料的轻重和沸点范围的宽窄。
A.恩式蒸馏
B.突沸点蒸馏
C.间歇蒸馏
D.平衡汽化
