疑难 ...请说明原因.
1.How happy the villager were when they watched the PLA fighters _______ nearer and nearer.
A.marched,B.marching C.to march
2.Don't you know the girl _______ the next song?
A.singing B.to sing C.sung
3.I've heard a lot about it,but I've never seen it ______here in our department.
A.used B.using C.to be used
4.He tried hard to make us ________ his suggestion.
A.supporting B.support C.to support
请说明原因.还有..