根据对话情景, 填入所缺的句子完成对话。

A: What beautiful pictures!

B: No, they're not pictures.  

A: Stamps?         

B: They are used for posting letters.

A:       

B: They were invented by an Englishman named Rowland Hill.

A:      

B: I've got more than 700 of them.

A: By the way, what are you going to be when you grow up?

B: I'm going to be a stamp designer.

A:       

B: I'm going to study art really hard and go to an art college.

A: I hope your dream can come true.

B: Thank you.