Final answer:
Despite Earth's abundance of water, only 4 percent is freshwater, of which 68 percent is in glaciers, making it inaccessible. Less than 1% of Earth's freshwater is available for human consumption, leading to critical shortages as demand from a growing population increases.
Step-by-step explanation:
The question of why access to drinking water is critical despite the large quantities of water on Earth can be addressed by understanding the distribution of water types on the planet. The correct answer to the provided multiple-choice question is option c. Only 4 percent of the total water on earth is freshwater, out of which 68 percent is found in glaciers. While the Earth's surface is covered by about 71% water, about 97% of this is saline water in the oceans. Freshwater represents only 2.5% of the total water, most of which is locked in ice sheets, icebergs, and glaciers. Consequently, less than 1% of freshwater is readily accessible as surface water for consumption by living organisms, including humans.
This scarcity of accessible freshwater is compounded by the increasing demands of a growing global population, where water usage has multiplied sixfold over the past century. Predictions indicate that by 2025, only half of the world's population will have sufficient access to clean water.
Protecting and efficiently managing our freshwater resources is crucial due to the limited availability of water that is suitable for human consumption without further treatment—such as desalination or rainwater harvesting. This situation underscores the importance of water conservation and finding sustainable methods to fulfill the water needs of communities worldwide.