下列合金铸造时，易产生缩松的铸造合金是（）
A.灰铸铁
B.锡青铜
C.低碳钢
D.铝硅合金
参考答案：B
—What would I do if I can't sleep before a big exam?
—You'd better a long walk before going to bed. [ ]
A. take
B. taking
C. to take
2013年，上海市与海南省百强企业总营业收入相差
A.36711.5
B.35711.5
C.34711.5
D.37711.5
