The correct pair(s) of the ambident nucleophiles is (are):
(A) AgCN / KCN
(B) RCOOAg / RCOOK
(C) AgNO$$_2$$ / KNO$$_2$$
(D) AgI / KI

An ambident nucleophile is a nucleophile that has two different nucleophilic sites through which it can attack. The key pairs to consider are those where the silver salt and potassium salt of the same anion react through different atoms.

(A) In the case of $$\text{CN}^-$$, the cyanide ion can attack through either carbon or nitrogen. $$\text{KCN}$$ typically gives cyanides (attack through carbon), while $$\text{AgCN}$$ gives isocyanides (attack through nitrogen). This demonstrates the ambident nature of $$\text{CN}^-$$.

(B) The carboxylate ion $$\text{RCOO}^-$$ has two equivalent oxygen atoms, but both give the same product (an ester). The silver and potassium salts do not produce fundamentally different products based on different nucleophilic sites, so this is not a typical ambident nucleophile pair.

(C) The nitrite ion $$\text{NO}_2^-$$ can attack through either nitrogen or oxygen. $$\text{KNO}_2$$ gives nitro compounds (attack through nitrogen), while $$\text{AgNO}_2$$ gives nitrite esters (attack through oxygen). This demonstrates ambident behavior.

(D) The iodide ion $$\text{I}^-$$ has only one nucleophilic site, so it is not an ambident nucleophile.

Therefore, the correct pairs of ambident nucleophiles are (A) and (C) only.