Answer:
They are located in the same region
They all border the state of Kentucky
They are Virginia's westernmost watersheds
Explanation:
Big Sandy, Clinch-Powell and Holston watersheds are all located in Virginia.
These watersheds are located in the west region of Virginia alongside the border with the state of Kentucky
They are located next to each other and all tree connect with Kentucky.
With their area they are not the smallest nor the largest watersheds in Virginia.
Big Sandy's area is 990 sq miles, Clinch-Powell's is 1.811 sq miles, while Holston watershed's area is 1322 sq.miles