It becomes D. Groundwater
Answer:
Industrial Revolution
Explanation:
In the 18th century, the industrial revolution took place. People started having more jobs than before and also getting paid for their labor. As the workers and employees were getting paid and jobs were available because of the industrial revolution, people started buying goods for their families. As a result, the standard of living also went up. Also, there was enough food for families to grow. As a result, the total population increased. In the 18th century, for the first time, the total population reached 1 billion landmarks.
2 and 3 are too similar to distinguish because they both are saying it's been back up on several different accounts but 3 seems like a more solid answer go with 3
