$A$ crystal diode is a:

Two statements are given below:
$A$. When the forward bias voltage across a $p-n$ junction diode increases above a certain threshold voltage,the diode current increases significantly.
$B$. This current is called reverse saturation current.
Choose the correct answer from the options given below:

$A$ realistic graph depicting the variation of the reciprocal of input resistance $(1/r_i)$ in an input characteristics measurement in a common emitter transistor configuration is:

Assuming in forward bias condition there is a voltage drop of $0.7 \text{ V}$ across a silicon diode,the current through diode $D_1$ in the circuit is . . . . . . $\text{mA}$. (Assume all diodes in the given circuit are identical)

The current through the ammeter (neglecting internal resistance) in the following circuit is

The resistance of a reverse biased $P-N$ junction diode is about