I'm pretty sure A is the answer...
I hope this is correct and helps!
A, colder climate the lower the pop density
The Midwest is sometimes referred to as the Breadbasket Colonies because in the Colonial times, the Midwestern states were the ones that grew wheat and crops to sell. The Mississippi River was extremely important in that region, especially to those who lived more inland, because farmers would use the port of New Orleans, which carried off water from the Mississippi into the Gulf of Mexico, to ship and sell their crops to other regions of the country or to near by islands such as Cuba.
Hope that helped :)
People who reside in Panama are called Panamanians.