沸腾钢在浇注前采用的脱氧剂是()
A.锰铁
B.锰铁与硅
C.铝与硅铁
D.铝与碳
参考答案:A
一 Whose notebook is this?
一 It _____ be Carla's. It has her name on it. [ ]
A. might
B. must
C. shouldn't
D. can't
雨后天晴,我们看到的彩虹是光的_________形成的。