In an atom,an electron of charge $(-e)$ performs uniform circular motion ($U$.$C$.$M$.) around a stationary positively charged nucleus with a period of revolution $T$. If $r$ is the radius of the orbit of the electron and $v$ is the orbital velocity,then the circulating current $I$ is proportional to:

• A
  $e^{1} r^{-1} v^{1}$
• B
  $e^{1} r^{1} v^{-1}$
• C
  $e^{1} v^{1} r^{-1}$
• D
  $v^{1} r^{1} e^{-1}$