I think it is important for kids to learn how to manage ____

I think it is important for kids to learn how to manage ____ money.
A.a B.an C.the D./
Both Kate's classroom and the teachers' office are on ___ eighth floor.
A.a B.the C.an D./
People can't live without ___ air.
A.aB./ C.an D.the
at noon 是固定搭配吗?

希望尽量详细.