磨床开车前应先检查各操作手柄是否已退到空档位置上，然后空车运转，再检查（）。
A、润滑部位是否有油
B、砂轮是否旋转
C、工件是否装夹好
参考答案：C
—I've got some wonderful news.We have been invited to the palace ball.
—Really？______.
A．I don't believe so
B．I believe not
C．I can't believe it
D．I don't believe it
善于治疗下部痹证之腰腿疼痛，属于寒湿所致者，最宜选用的药物是( )
A．独活
B．络石藤
C．秦艽
D．防己
E．稀莶草
