Explanation:

In varactor diode the applied reverse bias controls the width and therefore capacitance of depletion layer. This capacitance is used for tuning. A tuning diode, also known as a varactor diode, variable capacitance diode, varicap diode or variable reactance diode, is a diode that has a variable capacitance which is a function of the voltage that is impressed on its terminals. Tuning / varactor diodes are operated reverse-biased, and therefore no current flows. Hence option 3rd is correct.