A student decided to silver-plate a locker key using the apparatus shown - VCE - SSCE Chemistry - Question 15 - 2002 - Paper 1

To determine the role of the key in the electroplating setup, we need to understand that in the process of electroplating, the key will serve as the cathode. The cathode is the electrode where reduction occurs and is typically connected to the negative terminal of the power supply, facilitating the deposition of metal onto the key as silver ions in the solution gain electrons. Therefore, the correct answer is:

D. cathode and is connected to the negative terminal of the power supply.