Your answer is 3! Hope you get a good grade :)♥
Answer:
Scientists debated the theories with each other and compared the theories with scientific observations
As glaciers melted at the end of the last Ice Age worldwide sea level increased immensely and river plains were flooded. Glaciers are floating bodies of ice. Ice is frozen water. When glaciers started melting water that had been frozen for decades or centuries was released back into the ocean. That lead to an increase in sea level. This also led to river plains being drowned/flooded. Therefore, the answer is 1 and 2.