why is there only 9 answers to trival pursuit on line when the challenge is 20 for today?

If you only answer 7 or the 9 questions correctly, you can replay until you get to 20.

There are never more than 9 questions for the daily game.  There are a few ways to do this…
 
1) If you are not current with the daily 9 wedges you can just do 3 different days
2) You can play the single player or multi-player game to complete the daily challenge
3) You can answer 7 questions correctly and 2 incorrectly so you can replay the game