5. In a certain table tennis singles competition, it was originally planned that each pair of players would play exactly one match, but after 3 players each played 2 matches, they withdrew. As a result, only 50 matches were played in total. Then, the number of matches played between these 3 players is
A. 0
B. 1
C. 2
D. 3
Let there be $n$ players besides the 3, and let the number of matches played among the 3 players be $x$. Since the 3 players have played a total of 6 matches, then $C_{n}^{2}+6-x=50 \Rightarrow C_{n}^{2}=44+x \Rightarrow n=10, x=1$. Therefore, the answer is $B$.