Between 1800 and 1930, the human population doubled from 1 billion to 2 billion. what led to this increase in population?

In the period between 1800 and 1930 the human population exploded, and it experienced its most rapid increase in population until then. There are several factors that contributed to this population increase, such as the improved healthcare, better nutrition, and better living conditions. The advancements in the medicinal field resulted in the usage of lot of new cures for diseases, so lot of diseases that were leading to prolonged illnesses or death were put under control or gradually eliminated. The malnutrition has always been a problem for the human kind, and lot of people have starved to death in the past, but during this period the food supplies significantly increased and were much more available, so the problem was largely solved in big portion of the world. The living conditions gradually improved as well as the industries and the cities were developing, so the people had easier lives of better quality.

answer; (b) medicare fee schedule;

i think the answer would be b.