What recent experimental evidence suggests that all animal appendages may be homologous?

The choices can be found elsewhere and as follows:

 A)recent changes in model analyses of the morphological features of animal phyla
 B)new tests on fossils for common ancestral appendage types across phyla
 C)the discovery of a regulatory protein for muscles in many different phyla
 D)the discovery of the "distal-less," or Dll, gene in many different phyla

I think the correct answer is option C. The recent experimental evidence would be the discovery of a regulatory protein for muscles in many different phyla. Hope this helped. Have a nice day.