Tom is a schoolboy.He is only seven years old, but he is very busy on weekdays.One Saturday he decided to relax himself, so he went to the cinema.

    It was the first time for him to do that.He bought a ticket and then went in.But after two or three minutes he came out, bought a second ticket and went in again.After a few minutes he came out again and bought a third ticket.Two or three minutes later he came out and asked for another ticket.Then the girl in the ticket office asked him, “Why did you buy so many tickets? How many friends did you meet?” Tom answered, “No, I have no friends here.But a big boy always stops me at the door and tears(撕) my ticket.”

读“长江剖面图”分析完成下列问题。

进入80年代，外债高达160亿美元，居东欧国家之首的是(     )