Which of the following is used as an oxidizing agent in volumetric analysis?

What weight of ferrous ammonium sulphate is needed to prepare $100 \, mL$ of $0.1 \, N$ solution? (mol. wt. $392$)

The required amount of crystalline oxalic acid (equivalent weight = $63$) to prepare $250 \, mL$ of $N/10$ oxalic acid solution is: (in $, g$)

Assertion : $K_2Cr_2O_7$ is used as a primary standard in volumetric analysis.
Reason : It has a good solubility in water.

$KMnO_4$ is titrated with ferrous ammonium sulphate hexahydrate in the presence of dilute $H_2SO_4$. The number of water molecules produced for $2$ molecules of $KMnO_4$ is $..........$.

When potassium permanganate is titrated against ferrous ammonium sulphate,the equivalent weight of potassium permanganate is