how do the similarities in the fore-limb nones of humans, cats, dolphins, and bats support the theory of evolu

Answer 1

they are homologous structures and suggest that we have a common ancestor. same goes for vestigial structures (tailbone, aopendix)

Answer 2

all have similar bone structures (2 bones in the forearm) but are very different otherwise. A biped, quadraped, swimmer and flyer. The fact that the bone structures are the same hints at a common evolutionary ancestor.

Answer 3

I think its called the pentadactyl limb. All mammals have the same structure of bones in their arms, just in different proportions

Here you go, wikipedia on the subject:

http://en.wikipedia.org/wiki/Evidence_of_evolution