Identify the reagents shown in bold in the following equations as nucleophiles or electrophiles
(a) `CH_(3)COOH + HO^(-) rarr CH_(3)COO^(-) + H_(2)O`
(b) `CH_(3)COCH_(3) + .^(-)CN rarr (CH_(3))_(2)C(CN)(OH)`
(c) `C_(6)H_(6) + CH_(3)overset(+)(C)O rarr C_(6)H_(5)COCH_(3)`