A:①②③
B:②③④
C:①③
D:②④
A: May____ come____, Nancy?
B: Yes,____ ____ come back now.
A: Thanks.
B: You're ____.
小黑熊爬到8米高的树顶,每次只能爬上2米,还要滑下1米,那么,它往上爬____ 次才能爬到树顶.