Observe the following statements :
$I$. The physical and chemical properties of elements are periodic functions of their electronic configuration.
$II$. Electronegativity of fluorine is less than the electronegativity of chlorine.
$III$. Electropositive nature decreases from top to bottom in a group.
The correct answer is :

• A
  $I$,$II$ and $III$ are correct
• B
  only $I$ is correct
• C
  only $I$ and $II$ are correct
• D
  only $II$ and $III$ are correct