The correct option is B Fe3+
Cr=1s2,2s22p6,3s23p63d5,4s1=[Ar]3d54s1
In d-block, Iron (Fe) has the configuration [Ar]3d64s2. If we remove 3 electrons, then it will be converted to Fe3+ with electronic configuration [Ar]3d5.
Fe3+=1s2,2s22p6,3s23p63d5,4s0=[Ar]3d5
Mn=1s2,2s22p6,3s23p63d5,4s2=[Ar]3d54s2
V=1s2,2s22p6,3s23p63d3,4s2=[Ar]3d34s2
hence, correct option is (b).