Hint: Think about the items required to play each sport.
This is the only sport which does not use a ball, it uses a shuttlecock.
Put the characters C - D - M - L - X in the right order...
...but not alphabetical.
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Hint: Think of Italy.
Answer: X - L - C - D - M.
These are the Roman numerals for 10, 50, 100, 500 and 1000, in ascending order.