根据对话内容补全单词。

　　A：It's ftartline　 1 ndline　 today，isn't it?

　　B：Yes，but it's btartline　 2 ndline　 warmer，Are you going s tartline　 3 ndline?

　　A：Yes，I am．Look at that notice!What does it say?

　　B：It says the ice on the lake is thin．

　　A：It's dangerous to skate otartline　 4 ndline　 the lake．I'm afraid we'd better tartline　 5 ndline　 skate today．