英语高手帮帮忙哟!~~帮我接一接一个句子
A:Hi,Lucy.Why do you look worried?
B:I look worried because I don't know the customs in Japan.You know I'll be an exchange student there.
A:Don't worry.let me tell you.__________________once.
B:What are they supposed to do when they meet for the first time?
........
参考答案:I have been there