Which of the following statements is correct regarding the gel electrophoresis technique?

• A
  $DNA$ fragments can be visualized in visible light without staining.
• B
  The natural polymer used as a matrix is extracted from sea weeds.
• C
  Bright blue-coloured bands of $DNA$ are seen in an ethidium bromide-stained gel when exposed to visible light.
• D
  The larger the $DNA$ fragment size,the further it moves in the agarose matrix.