Answer:
D.
Explanation:
None of the answers really make sense. A civilization would most likely engage in trade when they are low on a resource (food, gold, weapons etc.) The answer is definitely not B. A could be correct just for the fact that if a country isolates themselves, then the may be in need of a resource, however if they purposefully isolate then they wouldn't be likely to trade. So A is out. C could also work because it times of wars, amends need to be made and sometimes that can be done with trading. Still I believe the most plausible answer of these 4 would be D. Hope this helps! :)
