Which of the following statement(s) is/are not true about the following decomposition reaction?

$2{\mathrm{KClO}}_{3}\to 2\mathrm{KCl}+3{\mathrm{O}}_{2}$

1. Potassium is undergoing oxidation

2. Chlorine is undergoing oxidation

3. Oxygen is reduced

4.  None of the species are undergoing oxidation or reduction

(a, b, c, d)
Write the oxidation number of each element above its symbol, then
$2\stackrel{+1}{\mathrm{K}}\stackrel{+5}{\mathrm{Cl}}{\stackrel{-2}{\mathrm{O}}}_{3}\to 2\stackrel{+1}{\mathrm{K}}\stackrel{-1}{\mathrm{Cl}}+3{\stackrel{0}{\mathrm{O}}}_{2}$
(a) The O.N. of K does not change, K undergoes neither reduction nor oxidation. Thus, option (a) is not correct
(b) The O.N. of chlorine decreases from +5 in KClO3 to -1 in KCl, hence Cl undergoes reduction.
(c) Since, O.N. of oxygen increases from -2 in KClO3 to 0 in O2, oxygen is oxidised.
(d) This statement is not correct because Cl is undergoing reduction and O is undergoing oxidation.