Which of the following acid has the same molecular weight and equivalent weight

We know that equivalent weight$=\frac{\mathrm{Molecular} \mathrm{Weight}}{\mathrm{Net} \mathrm{positive} \mathrm{valence}}$

In the case of ${\mathrm{H}}_3{\mathrm{PO}}_2$ net positive valence=1

Therefore, ${\mathrm{H}}_3{\mathrm{PO}}_2$ has the same molecular weight and equivalent weight.

Hence, option(a) is correct.