The correct answer is B.
Desalination technology allows to obtain fresh drinking water from sea water (or saltwalter), by removing its former salty mineral components. This process also generates a by-product: salt.
Desalination requires very high energy consumption levels, and therefore it is very costly if compared to simply obtaining fresh water from groundwater (rivers, lakes) or water recycling. Moreover, it is said that the taste of desalinated water is not very good either.