serves as a long-term storage area for water or nutrients.

A Reservoir

Explanation:

The Reservoir is a part of the biosphere that serves as a storage unit for nutrients or water for a long term. it serves as a long haul stockpiling zone for water or nutrients. An example can be a counterfeit lake, stockpiling lake built using a dam or bolt for the storage of water.

A reservoir is simply the storage space for fluids.

answerassignment page;

answer(b) keep oxygenated and deoxygenated blood separate;