在C盘当前文件夹下有一个已建立好的顺序文件Alph.txt，文件内容为只含有字母的一个字符串(有双引号界定符)。单击窗体，打开Alph.txt文件，读取字符串并显示在文本框Text1中，然后调用StrSort过程将此字符串按ASCII码的顺序重新排列并显示在文本框Text2，最后将重新排列的字符串存入AlpO.txt文件中(无双引号界定符)。请选择横线处合适的语句 ( )。
Private Sub Form_Load()
Dim StrIn As String, StrOut As String
Open "C:\ Alph.txt" For Input As #1
______
Close
Text1.Text=StrIn
______
Text2.Text=StrOut
Open "C:\ AlpO.txt" For Output As #2
______
Close
End Sub
Private Function StrSort(s As String) As String
Dim sArr() As String *1, i As Integer, j As Integer, n As Integer
Dim t As String*1
n=Len(s)
ReDim sArr(n)
For i= 1 To n
sArr(i) = Mid(s, i, 1)
Next i
For i=1 To n-1
For j=i+1 To n
If sArr(i) ＞ sArr(j) Then
t=sArr(i): sArr(i)=sArr(j):sArr(j)=t
End If
Next j, i
For i=1 To n
StrSort = StrSort & sArr(i)
Next i
End Function

A．Input #1, StrIn StrIn Print #2, StrOut

B．Input #1, StrIn StrSort(StrIn) Print #2, StrOut

C．Input #2, StrIn StrSort(StrIn) Print #1, StrOut

D．Print #1, StrIn StrSort(StrIn) Input #2, StrOut