The highest thermal diffusivity is of
Thermal diffusivity is the thermal conductivity of the material divided by the product of density and specific heat capacity, at constant pressure.
Thermal difference = k/(density × heat capacity) = 46.33/(0.26 × 0.12) = 1484.93
Thermal difference = k/(density × heat capacity) = 20.39/(0.41 × 0.032) = 1554.12.
Hence the highest thermal diffusivity from the given option is of Lead.