An engineer can design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. The actual forelimbs of these mammals do NOT seem to be optimally arranged because .

Natural selection

Explanation:

Forelimb provides body support during sitting or walking and absorption of impact forces during landing

Forelimbs carry the weight because of the angle between the stifle and hock in case of horsesForelimbs of whales helps in swimming whereas that of bats helps in swimming in the airThe actual forelimbs of these mammals do not seem to be optimally arranged because natural selection is generally limited to modifying structures that were present in previous generations and in previous species