Consider the two following statements $A$ and $B$,and identify the correct choice given in the answers :
$(A)$ In photovoltaic cells the photoelectric current produced is not proportional to the intensity of incident light.
$(B)$ In gas-filled photoemissive cells,the velocity of photoelectrons depends on the wavelength of the incident radiation.

• A
  both $A$ and $B$ are true
• B
  both $A$ and $B$ are false
• C
  $A$ is true but $B$ is false
• D
  $A$ is false but $B$ is true