I think that the best answer is C, it is not influenced by economic conditions.
I hope this helps!
One thing that separates us from the other animal classifications is that we have hair, everywhere! :D The next major difference is the fact that mammals don't lay egg's, we give birth to live creatures. Those are the 2 biggest things that distinguish us from them.
Hope I helped. :)
The four have molecular similarities, but have their own unique traits.
