What could an archeologist infer from the fact that fish bones have been found at mountain sites of the inca empire, while potatoes, a mountain crop, have been found at coastal inca sites?

Based on the information provided in this passage, an archaeologist could infer that different regions of the Inca Empire traded with each other. The fact that various agricultural products from different regions can be found across the Inca territory is evidence of the practice of trade that was carried out throughout the Empire. The Empire was able to do so despite the difficult terrain where it was located and the lack of large animals for transportation.

c) troops march forward in close formation against newer, more accurate weapons

what do you mean