【单选题】

设有如下程序：

Private Sub Command1_Click( )
Dim sum As Double, x As Double
sum = 0
n = 0
For i = 1 To 5
x = n / i
n = n + 1
sum = sum + x
Next
End Sub
该程序通过For循环计算一个表达式的值，这个表达式是()
A.1+1/2+ 2/3+3/4+4/5
B.1+1/2+2/3+3/4
C.1/2+2/3+3/4+4/5
D.1+1/2+1/3+1/4+1/5