A party is attended by twenty people. In any subset of four people, there is at least one person who knows the other three (we assume that if $X$ knows $Y$, then $Y$ knows $X$). Suppose there are three people in the party who do not know each other. How many people in the party know everyone?\\
(A) 16\\
(B) 17\\
(C) 18\\
(D) Cannot be determined from the given data.