In this tournament format, there will be 18 matches to determine the semi-finalists (since 18 teams in a knockout leads to 18 matches), and then an additional three matches in the semi-finals and finals (two semi-finals and one final), making a total of 21 matches.

Find the next two terms of the series:
The given series is: \( A, C, F, J, ? \).
(A) O
(B) U
(C) R
(D) V
Choose the correct answer from the options given below: