【单选题】

编写如下事件过程：

Private sub sub1ByVal x1As String, y1As String)
Dim xtAs String
Dim iAs Integer
i = Len(x1)
Do While i＞= 1
xt = xt + Mid(x1, i, 1)
i=i-1
Loop
y1 = xt
End Sub
Private Sub FormClick()
Dim s1As String, s2As String
s1= "teacher"
sub1 s1, s2
Print s2
End Sub
程序运行后，单击窗体，则窗体上显示的内容是
A．rehcaet
B．tahreee
C．themee
D．eerthea