A: Hey, Lisa! My friends and I were just sharing memories of junior high school.

B: Wonderful, Frank. ____

A: It's so cool. I think it has been fun. Do you think so?

B: Yeah! I've enjoyed every year of junior high school.

A: ____

B: Of course, I do. One of my memories is that I lost my watch in Grade 7. ____

A: Did you find it at last?

B: ____ Sam helped me find it. I was so thankful.

A: Oh. I remember my P.E. teacher best.

B: ____

A: Mr. King. He gave us clear instructions so that we'd be safe when playing sports.

B: I think he was really perfect.

在下面一段文字横线处补写恰当的语句，使整段文字语意完整连贯，内容贴切，逻辑严密。每处不超过15个字。

    古建筑是珍贵的文化遗产。____，一旦毁坏则不可能复原。古建筑能激起人们的民族自尊心和文化认同感，每个民族的人民都会为拥有世界级的文化遗产而感到无比自豪。然而，____，比如，在城市开发建设中，古建筑常常受到惊人的破坏，因此，____。