从方框中选择正确的单词或短语，将其适当形式填在空白处，使对话完整、正确。

go,    be,    experience,    come back,  activity

A: Hi, Paul. Long time no see! Nice to see you again. Did you have a good holiday?

B: Yes, I did.

A: Where have you been?

B: I have  to Mount Tai with my parents. It's a beautiful place.

A: When did you  from there?

B: Yesterday afternoon. What about you, Mike?

A: I have taken part in some social  during the holiday.

B: What have you done?

A: I have been a volunteer in the old people's home.

B: What a wonderful !

A: Yes, it was. Though I had no time to travel, I still felt very happy.

B: By the way, where is Helen?

A: She has to Shanghai to be a volunteer, and she will be back tomorrow.