Answer:
1. There is improved medical knowledge which makes people live longer with better medicines.
2. Better standard of living. The middle-class was increasing and people moved to cities. Fewer people starved and more access to technologies.
3. New technologies. Better farm equipment led to more food being produced. With more food, people could live longer.
4. Improved sewer systems/sanitation. Back then people threw their wastes out on the streets. This caused diseases and many children can not make it to adulthood.
5.A better understanding of science and other subjects. Scientists developed vaccines and antibiotics to fight diseases and improve human health.