Ethidium bromide is used as a stain in visualising DNA during gel electrophoresis because-
I. It intercalates between stacked base pairs and fluoresces
when exposed to UV.
II. It decreases the twist of the helix and increases the writhing
number of helix affecting its migration through the gel.
III.In the presence of non saturating amount of Ethidium
negatively supercoiled circular DNA migrates rapidly.
(a) All the above are true.
(b) Only I and II are true.
(c) Only I is true.
Only II and III are true.