Riddle #83

Question: There was once three trees. The first tree did whatever the third tree did, and the third tree did what ever the second one does. What happens if tree number two gets cut down?

Question: What do you call a sad bird?

Question: What kinds of balls do dragons play soccer with?

Question: What can be broken but never forgotten?

Question: What tastes better than it smells?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?