Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: In the photoelectric effect,the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface.
Reason $R$: When the photon of any energy strikes an electron in the atom,transfer of energy from the photon to the electron takes place.
In the light of the above statements,choose the most appropriate answer from the options given below:

• A
  Both $A$ and $R$ are correct but $R$ is $NOT$ the correct explanation of $A$
• B
  $A$ is correct but $R$ is not correct
• C
  Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$
• D
  $A$ is not correct but $R$ is correct