black and white caps problem

3 black caps and 2 white caps randomly 3 caps are chosen and A,B,C are made to wear they are standing in que and A can see B nC , B can only see C and C cant see anyone A is asked which cap are you wearing? Ans from A was he don't know
B was asked which cap is he wearing? B answered I don't know But when asked C , he gave the correct answer.

The question was...which color cap was C wearing?

 

Solution

When A says he doesn't know it means that he doesn't see two white caps. That means he sees
1. Two black caps
OR
2. One white cap and one black cap
In that context B knows that he's wearing a black cap if he sees C wearing a white cap. If B were to see C wearing a black cap he (B) wouldn't know the color of his cap. That is based on implications from A's answer.
Since B says he doesn't know the color of his cap it means that C wears a black cap.