The archeologists' discoveries indicate that Harappan cities had a common authority that governed their trade (C).
This is evident when you consider that the weighing blocks and trade seals from all over the Harappan territory were similar, meaning there was a common standard. This guaranteed:
- that the merchandise could be weighed according to the same reference everywhere (the common weighing blocks),
- and that thanks to nearly-identical seals marking the merchandise, external trading partners would recognise it as Harappan goods in general and not goods coming from certain particular cities.
For these standards to be put in place, there needed to be a an authority whose power spanned over all Harappan cities and ruled their trade.