The correct answer is c
A. Early citizens were founding by building rivers. The civilisations did not build rivers, they setteled near them.
B. Early civilisations used rivers for bounderies between countries. Though the rivers were in different countries, there is no evdience that they were used as borders.
C. Early civilisations were founded in major river valleys. The civilisations were founded in river valleys, and the rivers are still well-known today.
D. Early civilisations interacted with each other frequently. The civilisations were in different countries, there is no way for them to interact frequently.
Overall, all evdience points to the answer B.