Dianna's Supplemental Tip - Level 13-5
Mostly, this level is about clearing out the middle to the ceiling until you have a clear shot at the 9th hole (but don't clear that one till the very last shot. Then start shooting the mystery bubbles. I know you risk hitting a bomb or an infected bubble, but if you do not shoot the mystery bubbles, you will not have a high enough score to pass the level.
Go one by one from the bottom up (or through the middle, even) and if you hit a bomb, either drop it or plug it and then keep on going. Sometimes, if you're close enough to the top or already have a high enough score, you can ignore the bomb and just watch your countdown. On the last countdown of the bomb, shoot to clear the 9th hole and watch them all drop.
It's actually a fun level to see the bubbles dropping and bouncing all over the place!