They actually don't know for sure what led to the decline but a lot of people believe that the Aryans invaded and conquered the Indus Civilization which would make sense because they were the next people group to live there. I hope this helps!
Answer:
Trading good was apart of the Colombian. Stuff like trading horses, sugar plants, Tabaco but not only goods it also came with disease
D. all answer choices are correct
I hope this helps brainliest please