氧在焊缝金属中的存在形式主要是（）。
A.FeO夹杂物
B.SiO2夹杂物
C.MnO夹杂物
D.Cao夹杂物
参考答案：A
— I would like you to talk about the Great Wall.
— I'm sorry, but _____ Jack _____ I have been there. [ ]
A. either; or
B. neither; nor
C. both; and
D. not only; but also
证券机构在何期限内上诉才有效
