磨削（）时容易产生磨削裂纹。
A.低碳钢
B.中碳钢
C.淬火钢
D.高速钢
参考答案：C
20.______ that caused him to serve dinner an hour later than usual.
A．It was we being late
B．It was our being late
C．It was we were too late
D．It was because we were late
表现右胁隐隐作痛，略有灼热感，口燥咽干，易怒，胸中烦热，头晕目眩，午后低热者属
A．气滞血瘀B．肝胆气郁C．肝胆湿热D．阴虚郁滞E．结石梗阻
