3 columns, show value of last one populated...

I have three columns (A, B, C) I want to show in Column D, the last column that has a value.

if column A is populated and B and C are not populated, return A
if column A and B are poulated and C is not poulated, return B
if column A. B, and C are populated, return C

This porbablly pretty simple, but I just cant get the combination correct. Thanks for your help in advance!

~J