下列数组声明正确的是()。

A.n=6 : Dim a (1 to n) as integer

B.Dim a(10) as integer : ReDim a(1 to 12)

C.Dim a() as single : ReDim a(3,6) as integer

D.Dim a() as integer : n=6 : ReDim a(1 to n) as integer