The correct option is
C Fe2+ >
Fe3+Size (ionic radius) of Fe2+ is more than the size (ionic radius) of Fe3+. 3 electrons are removed from Fe to form Fe3+ and 2 electrons to form Fe2+, The ratio of the number of protons to the number of electrons is higher for Fe3+ than for Fe2+. Hence due to higher effective nuclear charge in Fe3+, the nucleus pulls the electrons to itself to greater extent than that in Fe2+ which results in a smaller ionic radius for Fe3+. Option C.