Consider the DataFrame df shown in the image below. Which of the following can return the head of the pivot table as shown in the image below df? df 0 world_rank 1 2 1 institution country Rank_Level Harvard University USA First Tier Top University Massachusetts Institute of Technology USA First Tier Top Unversity Stanford University USA First Tier Top Unversity University of Cambridge United Kingdom First Tier Top Unversity California Institute of Technology USA First Tier Top Unversity 2 3 3 4 pivot table median Rank_Level First Tier Top Unversity Other Top Unversity Second Tier Top Unversity Third Tier Top Unversity All country Argentina NaN 44.390 NaN NaN 44.390 Australia 48.055 44.580 49.125 47.285 44.765 Austria NaN 44.630 Belgium 51.875 44.715 49.600 46.890 46.210 Brazil NaN 44.380 NaN 47.030 44.690 NaN 44.365 49.565 df.pivot_table(values='score', index='Rank_Level', columns=' country', aggfunc=[np. median] Odf.pivot_table(values='score', index='country's columns='Rank_Level', aggfunc=[np. median], margins=True) df.pivot_table(values='score', index='Rank_Level', columns='country', aggfunc=[np.median), margins=True) Odf.pivot_table(values='score', index='country's columns='Rank_Level', aggfunc=[np. median])