“复盐”是指由多种简单阳离子和一种酸根离子组成的盐，如KAl(SO₄)₂；而由一种金属离子与多种酸根离子构成的盐则称为“混盐”，如氯化硝酸钙[Ca(NO₃)Cl]。下列化合物属于混盐的是 [ ]

A. CaOCl₂

B. (NH₄)₂Fe(SO₄)₂

C. BiONO₃

D. K₃[Fe(CN)₆]

If we _______ adequate preparations, the conference wouldn't have been so successful.[ ]

A. haven't made

B. wouldn't make

C. didn't make

D. hadn't made