Dim min As Single ,  d2 As Double , abc As String

则变量min的类型是({#blank#}1{#/blank#}) ，变量d2的类型是({#blank#}2{#/blank#}) ，变量abc的类型是({#blank#}3{#/blank#})。

A.可变类型   B.单精度型   C.双精度型   D.字符串型

Private Sub Command1_Click()

  Dim a(0 To 5) As Integer

  Dim i As Integer               ’①

  a(0) = 1                      '②

  For i = 1 To 5

    a(i) = 2 * a(i - 1) + 1          '③

  Next i

  Text1.Text = Str(a(6))         '④

End Sub

s = "2019.06 Visual Basic 6.0": n = 0 For i = 1 To Len(s)

    ch = Mid(s, i, 1)

    If ch >= "0" And ch <= "9" Then

        m = Asc(ch) - Asc("0") + 1

        a(m) = a(m) + 1

    End If

 Next i

 For i = 1 To 10

    If a(i) > 1 Then n = n + i

 Next i

数组 a 各元素的初始值都为0，执行该程序段后，则变量n的值为（  ）