（加试题）某程序代码如下：
Private Sub Command1_Click()
Dim c  As Integer
Dim a(1 To 20) As String
s = "123 how are you": c = 0
For i = 1 To Len(s)
a(i) = Mid(s, i, 1)
Next i
For i = 1 To Len(s) - 1
For j = Len(s) To i + 1 Step -1
If a(j) < a(j - 1) Then
k = a(j): a(j) = a(j - 1): a(j - 1) = k
End If
Next j
Next i
For i = 1 To Len(s) - 1
If a(i) < a(i + 1) Then c = c + 1
Next i
Text2.Text = Str(c)
End Sub程序运行结束后,变量c的值是（ ）

A．13

B．11

C．10

D．15