单选题   运行下列程序，窗体中的显示结果是：______。
    Option Compare Database
    Dim x As Integer
    Private Sub Form_Load()
    x=3
    End Sub
    Private Sub Command11 Click()
    Static a As Integer
    Dim b As Integer
    b=x^2
    funl x, b
    funl x, b
    MsgBox'x='＆x
    End Sub
    Sub funl(ByRef y As Integer, ByVal z AS Integer)
    y=y+z
    z=y-z
    End Sub