The Triangle Trade brought labor for a <em>very</em> cheap price, much much cheaper than indentured servants. They also began to use the triangle trade instead of enslaving the locals because the natives knew their way around the land and could run away easily.
The earliest civilization before the Incas, I believe to be the Andeans, so D none of the above.
Math was used to help the researchers with their tools and theories.
I think a to capture the attention of his listeners, who may have been doing ither things.