The diode used in the circuit shown in the figure has a constant voltage drop of `0.5 V` at all currents and a maximum power rating fo `100` milliwatts. What should be the value of the resistor `R`, connected in series with the diode for obtaining maximum current?
A. `1.5 Omega`
B. `5 Omega`
C. `6.67 Omega`
D. `200 Omega`