(a) Most liquids that conduct electricity are solutions of acids, bases and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
Acids produce the hydrogen ion (H+) while bases produce the hydroxide ion (OH-) when dissolved in water. These ions in water act as charge carriers and can hence help the acids and bases to conduct electricity. Salts produce both cations and anions when dissolved in water, which are conducting particles. Hence salts conduct electricity.
The passage of an electric current through a conducting solution causes chemical effects. That may cause formation of bubbles of a gas on the electrodes, deposition of metal on electrodes, changes of colour of solutions etc.
As copper ions are positive ions, hence they get deposited on the plate connected to the negative terminal of the battery.
Electroplating is the process of applying a metal coating on another piece of metal or on another conductive surface through an electro-deposition process.