Explanation

(d)
When chlorine reacts with dilute and cold NaOH sodium chlorine and sodium hypochlorite are formed.
2NaOH(cold) +Cl_{2}⟶NaCl +NaClO +H_{2}O
Sodium
hypochloride
Let oxidation state of Cl in NaCl is $x$
+ 1 +$\ x\$=0
X = -1
Let oxidation state of Cl in NaClO is $x$.
NaClO
+1 + $x\$- 2=0
$x$ - 1=0
$x\$= + 1
$\therefore\$oxidation states of chlorine changes from 0 to -1 and +1.