What conclusion would be mostappropriate about the genetic variation between humans and the three apes as illustrated by the phylogenetic tree

I believe the correct answer is that The genetic variation between humans and orangutans is the greatest. 
We cannot say that there is no genetic variation at all, because there obviously is - we are not the same as the other three apes, even though we have a common ancestor. Also, we cannot say that we are completely the same, because there are obvious differences. And finally, we didn't originate from those three animals, but rather all of us come from the same organism.