The reconstruction
The most difficult task confronting many Southerners during Reconstruction was devising a new system of labor to replace the shattered world of slavery. The economic lives of planters, former slaves, and nonslaveholding whites, were transformed after the Civil War.
I'd go with C, D and F. The main causes of population growth had to do with diet and hygiene and health care.
The Agricultural Revolution (which started in the 17th century) led to better food production and thus better diet and nutrition for people, so healthier lives.
The Industrial Revolution (beginning in the mid 18th century) pushed cities to create better sanitation methods to avoid cholera and other disease epidemics.
And the ongoing advances in medicine ever since the Scientific Revolution were doing their part also to increase lifespans.
The answer is blood because you might find in in certain bibles
various religious groups fleeing persecution in europe
