Rank the members of each of the following groups of species in the order of basicity, nucleophilicity,

Question:

Rank the members of each of the following groups of species in the order of basicity, nucleophilicity, and leaving-group ability. Briefly explain your answers.
(a) H2O, HO-, CH3CO2-;
(b) Br-, Cl-, F-, I-;
(c) -NH2, NH3, -PH2;
(d) -OCN, -SCN;
(e) F-, HO-, -SCH3;
(f) H2O, H2S, NH3.