Why do scholars believe that the Indus Valley had a highly developed civilization? A. It left behind many written records. B. Its cities show a high level of planning. C. It had a highly organized religion. D. Its royal tombs hold many artifacts.

B. Its cities show a high level of planning

Explanation:

Schoolars believe that Indus Valley had a highly developed civilization because there are ruins of thousands of cities and towns which show evidence of strong central planning and organization. For example: defense walls, protection from flooding, trash disposal systems, organized roads, advanced system of weights and measures and engaged in extensive trade

I believe the answer is A