$10 \ cm^{3}$ of $0.1 \ N$ monobasic acid requires $15 \ cm^{3}$ of sodium hydroxide solution whose normality is: (in $N$)

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Permanganate titrations are not performed in the presence of hydrochloric acid.
Reason $R$: Chlorine is formed as a consequence of the oxidation of hydrochloric acid.
In the light of the above statements,choose the correct answer from the options given below.

Estimation of $CO$ is done by using:

Which of the following reagents is not used in qualitative and quantitative chemical analysis?

$A$ $2.0 \, g$ sample containing $MnO_2$ is treated with $HCl$ liberating $Cl_2$. The $Cl_2$ gas is passed into a solution of $KI$ and $60.0 \, mL$ of $0.1 \, M \, Na_2S_2O_3$ is required to titrate the liberated iodine. The percentage of $MnO_2$ in the sample is $.....$ (Nearest integer).
[Atomic masses (in $u$): $Mn = 55, Cl = 35.5, O = 16, I = 127, Na = 23, K = 39, S = 32$]

Below are two statements. One is labeled as Assertion $(A)$ and the other as Reason $(R).$
Assertion $(A):$ When using an aqueous solution of $KOH$ in a volumetric analysis,its concentration should be checked before use.
Reason $(R):$ $KOH$ solution absorbs atmospheric $CO_2$ when it gets old.
In the context of the above statements,choose the correct answer from the options given below: