A chloride salt solution acidified with dil. HNO$$_3$$ gives a curdy white precipitate, [A], on addition of AgNO$$_3$$. [A] on treatment with NH$$_4$$OH gives a clear solution, B.

A chloride salt solution acidified with dilute HNO$$_3$$ gives a curdy white precipitate [A] on addition of AgNO$$_3$$, and [A] on treatment with NH$$_4$$OH gives a clear solution B.

When AgNO$$_3$$ is added to a chloride solution acidified with dilute HNO$$_3$$, silver chloride precipitates according to the reaction:
$$\text{Ag}^+ + \text{Cl}^- \rightarrow \text{AgCl} \downarrow \text{ (curdy white precipitate)}$$
This shows [A] is AgCl.

Treatment of AgCl with NH$$_4$$OH leads to formation of the diamminesilver(I) complex by the reaction:
$$\text{AgCl} + 2\text{NH}_3 \rightarrow [\text{Ag}(\text{NH}_3)_2]\text{Cl}$$
This gives a soluble complex and identifies [B] as [Ag(NH$$_3$$)$$_2$$]Cl (diammine silver(I) chloride).

Since [A] is AgCl and [B] is [Ag(NH$$_3$$)$$_2$$]Cl, the correct answer is Option C: AgCl & [Ag(NH$$_3$$)$$_2$$]Cl.