一个的φ300+0.050mm的孔在同一个钻床上经钻削、扩削和铰削（）加工而成。
A.三个工序
B.三个工步
C.三次进给
参考答案：B
—Have you worked here since you graduated?
—No, I ________ at a factory in Beijing for six years.
A．would work
B．have worked
C．had worked
D．worked
维持担保比例超过200%时，客户可以提取保证金可用余额中的现金或冲抵保证金的有价证券。( )
