6. In a certain singles table tennis tournament, it was originally planned that each pair of players would play one match, but after three players each played two matches, they withdrew from the tournament. As a result, only 50 matches were played in total. The number of matches played between these three players is
A. 0
B. 1
C. 2
D. 3
Let the number of matches between the 3 players be $x$, then the number of matches between these 3 players and the other players is $6-2x$, thus $C_{n-3}^{2}+6-x=50$. And $C_{10}^{2}=45 \Rightarrow x=1$, so the answer is $B$.