单项选择题
A.Mn;V;Nb;C;Si;B;Ti;Al;Zr B.Mn;Si;C;V;Nb;B;Al;Zr C.Mn;Si;C;V;Nb;Al;Ti;B;Ar
A.η=1/φ B.η=φ C.η≠φ
A.液态收缩+凝固收缩+固态收缩 B.液态收缩+凝固收缩 C.固态收缩+凝固收缩