E is incorrect because the conclusion is about whether language skills were needed to create the tools that Neanderthals made. The conclusion says nothing about the tools made by humans living at the same time as Neanderthals. E is not relevant.
C is correct because if the tools made in the experiment were much simpler than those made by Neanderthals, then the tools made in the experiment would not be comparable to those made by Neanderthals. Since the tools would not be comparable comparable, we could not use the experiment to draw any conclusions about the Neandrethals' tools. The undergraduates did not need verbal instructions to make their simple tools, but if the Neanderthals' tools were more complicated then making them may have required verbal instruction.