Which of the following systems of trade was most widely used in ancient river civilizations? bartering

b
the exchange of coined money

c
free exchange

d
international trade
HURRY PLZ!!

Aguiding principle of the national response framework is that: a. response partners use nonstandard structures to allow for flexible and scalable responses. b. unity of effort results when responding agencies are willing to relinquish their authorities. c. effective partnership relies on engaging all elements of the whole community. d. readiness to act encourages response partners to self-dispatch to an incident scene.