在窗体 Form1 上画一个名称为 Command1 的命令按钮,编写如下程序代码: Private Type stu sn As String * 20 class As String * 20 End Type Private Sub Command1_Click() Dim s As stu Open "c:allstu.dat" For Random As #1 Len = Len(s) s.sn = "John" s.class = "Computer 2013" Put #1, , s Close #1 End Sub 则以下叙述中正确的是 ________ 。