Answer:
"Were tied closely to the natural world."

This sentence gives no reason to add any commas what so ever. This would be a straight forward run-on sentence that would need no clause, pauses or anything that would break this sentence down any more.
Option B would give clear and straight forward information. The first option broke this sentence down as we can see, and as for this, this would not be the proper way of expressing this sentence. Therefore, your
last option would then be your answer.
The beginning of the "Solid South" for Democrats really starts during the Reconstruction period (the time period right after the Civil War). There were several reasons behind this support of the Democratic party. One of the largest ones was the policies of the Republican president (Abe Lincoln) right before the southern states seceded. Along with this, their priority on individual rights and little government interference resulted in a loyalty that was unmatched during this period.
Darwin's theory of evolution was controversial in the 1800's because it contradicted the biblical view of creation. So the answer is B. I hope this helps :)