Which of these excerpts from Dr. Seuss's book Bartholomew and the Ooobleck uses onomatopoeia?

1. But before Bartholomew could stop him, the Captain was leaning out the window, scooping up some oobleck on the end of his sword.
   
2. As he ran he could hear the "Plop! Plop!" of the oobleck on the windowpanes. It was pelting against the palace walls as big as greenish cup-cakes now!
   
3. "And it's going to keep on falling," he shouted, "until your whole great marble palace tumbles down! So don't waste your time saying foolish magic words."
   
4. "I don't know. And I hate to leave you stuck to your horn. But if you can't warn the people of the kingdom, I've got to find someone who can!"
   
5. "I mean," said Bartholomew, "this is all your fault! Now, the least you can do is say the simple words, 'I'm sorry.'"