Which of the following phenomena exhibits the particle nature of light?

In the photoelectric effect,electrons are emitted from a metal surface only when the incident light has a certain minimum . . . . . . .

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A :$ In photoelectric effect,on increasing the intensity of incident light,the stopping potential increases.
Reason $R :$ Increase in intensity of light increases the rate of photoelectrons emitted,provided the frequency of incident light is greater than threshold frequency.
In the light of the above statements,choose the correct answer from the options given below:

The curve between current $(i)$ and potential difference $(V)$ for a photo cell will be:

For photoelectric emission, tungsten requires light of $2300 \mathring{A}$. If light of $1800 \mathring{A}$ wavelength is incident, then emission:

Which of the following shows the particle nature of light?