C. They exchanged culture, trade, plants, diseases, and many other valuables across continents
<span>because the brass buttons on their uniforms looked like the flour dumplings or dough cakes </span>called<span> "</span>doughboys<span>", or because of the flour or pipe clay which the </span>soldiers<span> used to polish their white belts. </span>
Painted pottery, carved stone vessels, and jewelry
The answer is: Time, organization, and size
As the length of contact increased, the more time you would spend with the groups. This often correlated with the increase in size of the organization (even though larger organization tend to develop its own members division and not all members would know one another)
The factors would probably being women who gave birth and women who took care of the house hold