Question

what action did the colonists take in september of 1774 in response to their issues with britain?
they began a series of meetings with native american tribes to build a power base
they forced the british to send all their troops home and barricaded ports against their return.
representatives from 12 colonies met at a continental congress in philadelphia
an emissary was sent to king george iii to tell him his policies were not working

Explanation:

In September 1774, in response to British policies (like the Intolerable Acts), representatives from 12 of the 13 American colonies (Georgia did not send representatives initially) gathered in Philadelphia for the First Continental Congress. This was a significant step in colonial organization against British rule. The other options are incorrect: there was no major coordinated meeting - building power base with Native Americans as described; the British troops were not forced to leave and ports barricaded in 1774 in that way; and no such emissary was sent to King George III with that message as the main action in September 1774. The Continental Congress was the key event.

Answer:

C. Representatives from 12 colonies met at a Continental Congress in Philadelphia