Correct Answer - C
Phenol is weakest Bronsted base as phenol after loosing `H^(+)` produces least stable conjugate acnd among the compounds. Oxygen has more electronegative than N. So. O-H bond is more potar and it has highest value of acvdic character. Since. phenol is more acidic that alcohol. therefore. phenol has the least tendency to swept a proton and hence It is weak Bronsted base. Hence. phenol is least basic among given four choices.