Concept:Rainwater is the original source that fills rivers, lakes, and groundwater.
It is the only process that adds new water to the Earth's ecosystem.
Explanation:Earth has about 71% water, but most is salty or frozen.
Fresh water comes from rain, rivers, lakes, and underground.
However, rainwater is the first source because all other sources depend on it.
Rivers get water from rain or melting ice. Lakes collect rain. Groundwater forms when rain seeps into the ground.
Without rain, these sources would dry up. Therefore, rainwater is the primary source of water.
Water harvesting saves rainwater and is an efficient method of water management.
Answer:B. Rain water