The correct answer is:
Colonists avoided the rugged, difficult Cumberland Gap.
The Cumberland Gap was long used by Native Americans, was brought to the attention of settlers in 1750 by Thomas Walker, a Virginia physician and explorer. The path was used by a team of frontiersmen led by Daniel Boone, making it accessible to pioneers who used it to journey into the western frontiers of Kentucky and Tennessee. It was very hard for colonists to go through mountains. The Indian Americans were the ones who discovered it.