Dave的妈妈在邀请她的朋友Mary来参加晚会，用A-F来表示她们的对话顺序。
(     ) 1. That's grert!I can come at seven o 'clock.
(     ) 2. Mary,can you come to my party on Saturday?
(     ) 3. When is it?
(     ) 4. Well,the party is on Saturday evening.
(     ) 5. It's at seven o'clock.
(     ) 6. I'm sorry, I can't,I have to visit my uncle on Saturday afternoon.