What is the function of an aquitard?

An aquitard serves the important function of being an impermeable layer that slows down or restricts the movement of water within the subsurface geological formations. By being relatively impermeable compared to surrounding layers, aquitards can effectively separate different aquifers, which are layers that can transmit water more freely. This characteristic makes aquitards crucial for maintaining the integrity of aquifers and influencing groundwater flow.

In contrast, the other options do not accurately describe the role of an aquitard. A conduit for transporting water refers to features such as wells or aquifers, while a zone of sand and gravel is more characteristic of an aquifer itself, which allows for significant water storage and transmission. Lastly, a measure of electrical current has no connection to the geological context of aquitards and aquifers, focusing instead on electrical principles. This reinforces the significance of option B as it aligns with the fundamental understanding of groundwater systems and the geological functions at play.