The color change from purple to colorless when the first addition of
was made was instantaneously. Option A is correct.
When
was added for the first time, the hue changed instantly from purple to colorless. This is due to the extremely quick reaction that occurs between
and the reducing agent, which is often an iron(II) ion.
So, The permanganate ion
which is reduced to the colorless manganese(II) ion
during the reaction, is responsible for the purple color of

Therefore, Option A is correct.