补全对话。

A：Alison, how long have you been 　　1　　?

B：I’ve been skating 　　2　　 five hours．

A：Wow!Sam, how long did you skate?

B：I skated for four hours．I started 　　3　　 nine o’clock 　　4　　 the morning and stopped at one o’clock in the afternoon．I’m very tired!

A：When did you start skating, Victor?

B：At nine o’clock．

A：so you’ve been skating for…

B：I’ve been skating for five hours．

A：How long did 　　5　　 skate, Celia?

B：Umm, let’s see…I skated for two hours．