Kentucky Association for Academic Competition (KAAC) Practice Test

The Big Sandy River is indeed significant in forming part of Kentucky's eastern border. It serves as a natural boundary between Kentucky and West Virginia, flowing into the Ohio River. This river is an important tributary that influences the geography and hydrology of the region.

The other rivers mentioned do play vital roles in Kentucky's landscape but do not form part of its eastern border. The Cumberland River primarily runs through the central part of the state, the Ohio River represents the northern boundary, and the Licking River flows through the northern region without forming the eastern edge of Kentucky. Understanding the geographical features of Kentucky helps in comprehending the state's boundaries and its relationship with neighboring states.