16. 10 athletes participate in a table tennis competition, where each pair of them plays exactly one match. There are no ties in the matches, the first place wins $x_{1}$ matches and loses $y_{1}$ matches; the second place wins $x_{2}$ matches and loses $y_{2}$ matches; ..; the tenth place wins $x_{10}$ matches and loses $y_{10}$ matches. If we denote $M=x_{1}^{2}+x_{2}^{2}+\ldots+x_{10}^{2}, N=y_{1}^{2}+y_{2}^{2}+\ldots+y_{10}^{2}$, then ( ).
( A ) $M<N$
( B ) $M>N$
( C ) $M=N$
(D) The relationship between $M$ and $N$ is uncertain
Reference answer: C
