为了提高钢的硬度和切削性能,对低碳钢和低碳合金钢大多采用()处理
A.退火
B.正火
C.淬火
D.回火
参考答案:C
He ______ be sitting at the gate, waiting for his lost son.
A.used to
B.was used to
C.could
D.was accustomed
天然的抗痛风药为()。
A.丙磺舒
B.别嘌醇
C.利福喷丁
D.甲氧苄啶
E.秋水仙碱