Two equal point charges are separated by a distance $d.$ When the separation is reduced to $\frac{d}{3},$ what happens to the force between the charges?

A it decreases by a factor of $3$

it increases by a factor of $3$

$($C$)$ it increases by a factor of $9$

it decreases by a factor of $9$

it increases by a factor of more than $16$