Q9 Answer
2 DIAMONDS
NORTH has a big hand - 22+HCP balanced or 20/21+ HCP unbalanced. If you have 0-6 HCPs your response is 2D (the waiting bid) Also you may have 8+ HCPs but no good bid (e.g. 4441 distribution.
Q19 Answer
3 NO TRUMPS
Your partner has opened and has 6 diamonds and lots of HCPs. You have 15 HCPs and all 4 suits have been bid so you should be in game. So should it be in diamonds or 3NT? 3NT is always better than a minor, so 3NT.
Q29 Answer
DOUBLE
What to do if your partner has bid 1NT and there is interference? DOUBLE if you have more than 7 HCPs or if you have 6 or less HCPs and a 5 card suit, then bid the suit.