窗体上有一个名称为Text1的文本框，一个名称为Command1的命令按钮。命令按钮的单击事件过程如下：
Private Sub Command1_Click()
Dim x1 As Integer, x2 As Integer, x3 As Integer
s=Trim(Text1.Text)
strLen=Len(s)
For i=1 To strLen
c=Mid(s，i，1)
Select Case c
Case "0" To "9"
x1=x1+1
Case "A" To "Z"
x2=x2+1
Case "a" To "z"
x3=3+1
Case Else
x4=x4+1
End Select
Next
Print "x1"; x1, "x2"; x2, "x3"; x3, "x4"; x4
End Sub
以下关于上述程序的叙述中，正确的是