What kind of $p-n$ junction diode does not require any kind of bias?

The following graph represents:

State the band gap of the semiconductor used in the making of $LED$.

In a $PN$ junction photocell,the value of the photo-electromotive force produced by monochromatic light is proportional to

The maximum rated power of the $LED$ is $2 \text{ mW}$ and it is used in the circuit with an input voltage of $5 \text{ V}$ as shown in the figure below. The current through resistance $R$ is $0.5 \text{ mA}$. The minimum value of the resistance $R_S$ to ensure that the $LED$ is not damaged is . . . . . . $\text{k}\Omega$.

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Photodiodes are preferably operated in reverse bias condition for light intensity measurement.
Reason $R$: The current in the forward bias is more than the current in the reverse bias for a $p-n$ junction diode.
In the light of the above statements,choose the correct answer from the options given below: