The primary standard solution for the estimation of $Na_2S_2O_3$ is:

$K_2Cr_2O_7$ is preferred to $Na_2Cr_2O_7$ for use in volumetric analysis as a primary standard because

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

Of all the three common mineral acids,only sulphuric acid is found to be suitable for making the solution acidic in redox titrations involving $KMnO_4$ because:

$30 \ mL$ of acid solution is neutralized by $15 \ mL$ of a $0.2 \ N$ base. The strength of acid solution is $.............. \ N$.

Given below are two statements
Statement $I$: Aqueous solution of $K_2Cr_2O_7$ is preferred as a primary standard in volumetric analysis over $Na_2Cr_2O_7$ aqueous solution.
Statement $II$: $K_2Cr_2O_7$ has a higher solubility in water than $Na_2Cr_2O_7$.
In the light of the above statements,choose the correct answer from the options given below: