A realistic graph depicting the variation of the reciprocal of input resistance in an input characteristics measurement in a common emitter transistor configuration is:

In a CE configuration, the input junction is the base-emitter junction, which behaves essentially like a forward-biased diode. The input characteristic is a plot of base current ($$I_B$$) versus base-emitter voltage ($$V_{BE}$$) for a constant collector-emitter voltage ($$V_{CE}$$).

The dynamic input resistance ($$r_i$$) is defined as the change in input voltage divided by the resulting change in input current:

$$r_i = \left( \frac{\Delta V_{BE}}{\Delta I_B} \right)_{V_{CE} = \text{const}}$$

$$\frac{1}{r_i} = \frac{\Delta I_B}{\Delta V_{BE}}$$

Below Cut-in Voltage ($$V_{BE} < 0.6\text{ V}$$): The base-emitter junction is not yet conducting significantly. The current $$I_B$$ is nearly zero, and the curve is flat. Therefore, the slope $$1/r_i$$ is zero.

Near Cut-in Voltage ($$V_{BE} \approx 0.6\text{ V}$$): The current begins to rise. The slope $$1/r_i$$ starts to increase from zero.

Above Cut-in Voltage ($$V_{BE} > 0.6\text{ V}$$): The current increases exponentially at first. However, in a realistic transistor, internal series resistances eventually limit the current's rate of increase. This causes the slope of the $$I_B$$ vs $$V_{BE}$$ curve to level off and approach a steady value at higher voltages.

All these are correctly shown in the figure in option (B)