What type of $p-n$ junction diode does not require forward bias to operate?

In a photodiode,the value of the $emf$ produced by a monochromatic light beam is directly proportional to

$A$ Light Emitting Diode $(LED)$ has a voltage drop of $2\,V$ across it and passes a current of $10\,mA$ when it operates with a $6\,V$ battery through a limiting resistor $R$. The value of $R$ is.........$k\,\Omega$.

The given graph represents $V-I$ characteristic for a semiconductor device. Which of the following statements is correct?

$A$ $CCD$ camera is fabricated using a semiconducting material having a band gap of $3 \ eV$. The wavelength of light it can detect is nearly (in $nm$)

Consider the following statements $A$ and $B$ and identify the correct answer:
$A$. For a solar-cell,the $I-V$ characteristics lies in the $IV$ quadrant of the given graph.
$B$. In a reverse biased $pn$ junction diode,the current measured in $(\mu A)$ is due to majority charge carriers.