Answer: Option C.
Nonconservative elements are non-reactive in seawater and have a short residence time.
Step-by-step explanation:
Non conservative elements are elements that enter the sea water and have little concentrations in the ocean and show spartial variationns. These elements have short residence time I .e short replacement time and they are non reactive .Constituents such as phosphate, nitrate, and other nutrients, and dissolved oxygen, carbon dioxide, etc. are non-conservative because their concentrations are later changed by chemical reaction in the sea.