不太理解哪位高手给解释一下

不太理解谁给解释一下？
Private   A         As   B               引用外部类B
Private   D         As   String

Public   Function   Initialize(ByVal   C   As   B)   As   Boolean       --->     解释一下这句该怎么理解
        On   Error   Resume   Next
Set   A   =   C                                           -----> 用C实例化？
        Initialize   =   True
End   Function
Public   Sub   Terminate()
        Set   A   =   Nothing
End   Sub

------解决方案--------------------
Private A As B 引用一个外部类B
Private D As String

Public Function Initialize(ByVal C As B) As Boolean ' 定义对象C为外部类B
On Error Resume Next
Set A = C -----> 实例化C的继承对象A
Initialize = True
End Function
Public Sub Terminate()
Set A = Nothing
End Sub
----------------------
简单一点(不考虑效率问题)可以这样:

Private A As New B

Public Sub Terminate()
Set A = Nothing
End Sub