Which of the following semiconductor devices requires a reverse bias to operate?

An $LED$ is manufactured using zinc selenide; then it emits:

Explain the design,working,uses,and benefits of a light-emitting diode $(LED)$.

The schematic symbol of a light emitting diode $(LED)$ is:

Three photodiodes $D_{1}, D_{2}$ and $D_{3}$ are made of semiconductors having band gaps of $2.5 eV, 2 eV$ and $3 eV$,respectively. Which one will be able to detect light of wavelength $600 nm$?

Assertion: $A$ $p-n$ junction with reverse bias can be used as a photo-diode to measure light intensity.
Reason: In a reverse bias condition,the current is small but is more sensitive to changes in incident light intensity.