Im guessing it is due to gene shuffling
The maximum probable speed of walking is restricted mainly by two factors, that is, the length of the leg and the free fall acceleration. The animals with longer legs exhibit higher maximum walking speed, while the animals with very short legs exhibit low maximum walking speed.
The large birds like pheasants usually walk brief distances, however, birds like chickadees never walk. In the case of pheasants, they exhibit a higher maximum walking speed, on the other hand, the chickadees exhibits a low maximum walking speed. Thus, the chickadees should never walk, they should fly or hop.
Also, more energy is utilized in flying than in walking. Therefore, large birds like pheasants usually walk brief distances so that energy can be saved.
I say A because the way the question is formatted it is clear that...
