Answer:
A. Ice sheets and glaciers
Explanation:
The majority of the freshwater on Earth is not actually in liquid form, but it is frozen. Around 87% of the total freshwater reserves are located in the ice sheets around the North Pole and South Pole, as well as the glaciers in close proximity tot he poles and the higher mountains. This is a big problem since only 13% of the freshwater reserves are in liquid form, 12% of which are groundwater, and only 1% being a surface water. Big portion of the surface water has been polluted, thus it is not good for usage, while the groundwater is constantly being depleted.
The freshwater reserves vary from period to period, and it depends a lot on the climate. In the periods when there's an ice age, the ice sheets and glaciers account for even higher percentage of the freshwater reserves, but in the warmer periods, the surface water and the groundwater increase.
