Of the two procedures just described, preparation and carboxylation of a Grignard reagent or formation and hydrolysis

Question:

Of the two procedures just described, preparation and carboxylation of a Grignard reagent or formation and hydrolysis of a nitrile, only one is appropriate to each of the following RX → RCO2H conversions. Identify the correct procedure in each case, and specify why the other will fail.
(a) Bromobenzene → benzoic acid
(b) 2-Chloroethanol → 3-hydroxypropanoic acid
(c) tert-Butyl chloride → 2, 2-dimethylpropanoic acid