Which of the following statement is true about electrolytes?
An electrochemical cell always needs an electrolyte.
Let us find the answer by the process of elimination:
A is false because it is not necessary that the electrolytes are always in solution or aqueous form. It is also possible to have electrolytes in the molten or fused form.
B is false because we can also have electrolytes made of weak acids and bases in this case they would be called weak electrolytes.
C is false because it is possible to have polar-covalently bonded electrolytes which would typically be weak electrolytes.
D is true. We always need an electrolyte in any type of cell for the transfer of ions and electrons through it, without the electrolyte the cell would not function.