Which of the following statements is correct?

a$)$ the $HCl$ solution added to the antacid is more than necessary to neutralize the antacid.

b$)$ the excess $HCl$ acid was titrated with $S_2{O}_3$ solution.

c$)$ Starch is the indicator.

d$)$ The change of color from pink to blue

Bleach analvsis

$18-$ A bleach sample was diluted $15$ times, if the molarity of the dilutec sample is $0\mathrm{.}056M,$ calculate the mass percent of NaClO in the original sample? $($Assume the density of the bleach $=1\mathrm{.}12\frac{g}{m}l($atomic masses $Na=23\mathrm{.}0,Cl=35\mathrm{.}5$ and $O=16\mathrm{.}0\frac{g}{m}ol)?$

a$)4\mathrm{.}55$

b$)5\mathrm{.}6$

c$)7\mathrm{.}0$

d$)6\mathrm{.}3$

$19-$ Sodium thiosulfate $(N{a}_{2}S{O}_3)$ act as $.........$ in bleach analysis experiment

a$)$ Reducing agent

b$)$ Oxidizing agent

c$)$ Self$-$oxide

d$)$ Self$-$redox