Answer:
D. Natural selection is generally limited to modifying structures that were present in previous generations and in previous species
Explanation:
Natural selection can be explained or described as a situation whereby the organisms that are more adapted to their environment are known to be more likely survive and transfer the heritable traits to their young ones through reproduction.
Therefore at the long run, the organisms with the most adapted features or traits will dominate that particular environment.
This means that, the adapted traits may be modified in the new organisms produced.
So, in this case, the engineer can easily design skeletal design that are more functional than those currently found in the forelimbs, since he is the one designing , he is capable of making his own decision on what and how he wants the skeletal design to look like, because it does not involve natural selection.