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