选择句子完成对话。 A. Can you skate backwards? B. Can you skate forwards? C. I fall down. D. Yes, I can turn around. E. I think I can stand up. A: Let's go skating! B: OK! Can you stand up on the ice? A: 1____________ Look! I'm standing. B: Oh! You can stand. 2____________ A: I think I can skate forwards. B: Good! 3____________ A: Sorry! I can't skate backwards. B: Can you turn around? A: 4____________ Oops! 5____________ B: Come on!