I am self studying and trying questions of quantitative aptitude in my mathematics exam and I am unable to solve this problem.
Of three persons $A$, $B$ and $C$, one always lies while the others always speak the truth. $C$ asked $A$, "Do you always speak the truth, yes or no?" He said something that $C$ could not hear. So, $C$ asked $B$. "what did $A$ say?" $B$ replied, "$A$ said No".
So, who is the liar?
The answer, supposedly, is
Unfortunately, I am completely clueless on how to approach this question. Any help would be really appreciated!