在铸铁焊补时，为了得到灰铸铁焊缝，可在焊缝中加入促进石墨化元素，如（）等。
A、镍Becareful,_______you'llfalldown.
Weregretto________thatitmaynotbepossibletodealwitheveryrequest.
________tothepapersisrestrictedtoDefenseDepartmentpersonnelonly.
唐代将"同中书门下平章事"基本固化为宰相名号始于()
Othersarguethatsincetheearthhasenduredalongstringoficeagesinthelasttwomilliontothreemillionyears,anywarmingis________tobetemporary.
