The basic character of oxides MgO, SrO, K2O, NiO, Cs2O increase in the order
MgO > SrO > K2O > NiO > Cs2O
Cs2O < K2O < MgO < SrO < NiO
NiO < MgO < SrO < K2O < Cs2O
K2O < NiO < MgO < SrO < Cs2O
Basic nature increases with increase in electropositive nature