单项选择题

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