Given below are four statements pertaining to the separation of $DNA$ fragments using gel electrophoresis. Identify the incorrect statements:
$(a)$ $DNA$ is a negatively charged molecule and so it is loaded on the gel towards the Anode terminal.
$(b)$ $DNA$ fragments travel along the surface of the gel,whose concentration does not affect the movement of $DNA$.
$(c)$ The smaller the size of the $DNA$ fragment,the larger is the distance it travels through it.
$(d)$ Pure $DNA$ can be visualized directly by exposing it to $UV$ radiation.
Choose the correct answer from the options given below:

• A
  $(a), (c)$ and $(d)$
• B
  $(a), (b)$ and $(c)$
• C
  $(b), (c)$ and $(d)$
• D
  $(a), (b)$ and $(d)$