<span>B. An abundance of natural resources including salt and gold</span>
Answer:
The slave trade had devastating effects in Africa. Economic incentives for warlords and tribes to engage in the slave trade promoted an atmosphere of lawlessness and violence.
The answer is A. Drove production costs up. It drove production costs down, because they were able to take less time to make the products as well as less materials because 1) standardized parts were invented around the same time, and 2) they didn't have people preparing everything so materials weren't wasted.
Im guessing they were called "wagon trains". Apologies if i'm incorrect!
A massive topic for this could be oil. You could talk about OPEC and the different types of technologies involved