用适当的词填空,把对话补充完整。 three, How much, on sale, Four yuan, welcome A: 1_______________ are the pens? B: Sixteen yuan. A: That's expensive. Are the books 2_______________? B: Yes. A: How much is the book? B: 3_______________. A: I'll take 4_______________, please. Thank you. B: You're 5_______________.