下列气体中,对钢的氧化加速最快的是()。
A.SO2
B.H2O
C.O2
D.CO2
参考答案:A
The play _______ for 10 minutes when we arrived at the theater. [ ]
A. had begun
B. has been on
C. had been on
D. began
蒸馒头时馒头发黄,可在锅中加入适量的(),再蒸一会儿后馒头就会变白。
A.醋
B.碳酸钠
C.碳酸氢钠