Answer: B. Nonconservative elements are reactive in seawater and have a short residence time.
Explanation: The non-conservative elements of seawater possess two paramount properties which include being chemically or biologically reactive as they are usually dependent on seasonal or short geological cycles. They also posses short residence time, which is the measure of the average time a dissolved substance spends in seawater. They also have varying concentration Ober time. Examples of nonconservative elements include; Iron and Carbon.