单击一次命令按钮后，下列程序的执行结果是
Private Sub Command1_Click()
s=P(1) + P(2) + P(3) + P(4)
Print s
End Sub
Public Function P(N As Integer)
Static Sum
For i=1 To N
Sum=Sum + i
Next i
P=Sum
End Function

A．15

B．25

C．35

D．45