在窗体中添加一个标签LblResult和一个命令按钮Command1，然后编写程序。程序的功能是单击命令按钮，计算1+2+3+4+5的值，并把结果转化为字符串显示在标签内，能够实现上述功能的程序段是， ( )

A．Private Sub Command1_Click() Dim I,R As Integer For I=1 To 5 Step 1 R=R+I Next LblResul Name=Str$ ( End Sub
B．Private Sub Command1_ClickO Dim I,R As Integer For I=1 To 5 Step 1 R=R+I Next LblResul Caption= Str$ ( End Sub
C．Private Sub Command1_Click() Dim I,R As Integer Do While I＜5 R=R+I I=I+1 Loop LblResul Caption=Str$ ( End Sub
D．Private Sub Command1_Click() Dim I,R As Integer Do R=R+I I=I+1 Loop While I＜5 LblResul Caption=Str$ ( End Sub