The correct option is B 3
The balanced chemical equation is:
10FeC2O4+6KMnO4+24H2SO4→5Fe2(SO4)3+20CO2+6MnSO4+3K2SO4+24H2O
n-factor of an ion in case of redox change=Change in oxidation state×Number of atoms undergoing this change per molecule
Fe2+→Fe3++e−
n factor for Fe2+ to Fe3+=3−2=1
C2O2−4→2CO2+2e−
n factor for C2O2−4 to CO2
=|4−3|×2=2
Overall n factor is 2+1=3.