Final answer:
We are currently using a substantial percentage of the world's reliable runoff for human activities, with agriculture being a major consumer. Water use is expected to increase, and the projected future percentage by 2025 is higher than what we are using now. The most likely answer to the question is A) 30%, 50%.
Step-by-step explanation:
The question asks what percentage of the world's reliable runoff are we using currently and what percentage are likely to be using by 2025. Reliable runoff refers to the part of rainfall that does not immediately evaporate or get absorbed into the groundwater, but instead flows across the land and into rivers, streams, and lakes - water that can be reliably accessed for use by humans.
Considering the available data on water use around the globe, there is a consensus that a significant amount of the available fresh water is being used for various human activities, particularly for agriculture which consumes about 70% of the fresh water. The world has been seeing an increasing demand in freshwater usage due to population growth and industrial activities. While specific percentages may fluctuate based on new studies and evolving consumption patterns, a sizable proportion of available fresh water is being utilized.
With the provided options and the projections for water use by 2025, it is estimated that currently we use a substantial percentage of the world's fresh water supply and by 2025 the demand will increase further. Option C) 20%, 40% is likely an underestimate. Based on the trends, we can deduce that the correct answer would be A) 30%, 50%, indicating a projected increase in water consumption as the population grows and demands on agriculture and industrial activities intensify.