[解析]
M:All right,Sarah,we know that you're planning something big for john's birthday.Could you tell us just what you have in your mind?
W:I wanted to make his birthday a very special event.John has a sister living in france.And I'll send her a plane ticket so that she can be here for his birthday.
M:Boy,what an excellent plan.That's something special.I kind of guessed you had some secret plan and were waiting for the right time to tell me.
W:Well,I didn't want to say anything until I was sure she could come.