题目

 Parents should stop blaming themselves because there’s not a lot they can do about it. I mean the teenager problem. Whatever you do or however you choose to deal with it, at certain times a wonderful, reasonable and helpful child will turn into a terrible animal. I’ve seen friends deal with it in all kinds of different ways. One strict mother insisted that her son, right from a child, should stand up whenever anyone entered the room, open doors and shake hands like a gentleman. I saw him last week when I called round. Sprawling himself（懒散地躺) on the sofa in full length,通过书籍、报刊、杂志和互连网，收集有关资料，说说什么是喀斯特地形？世界哪些国家有喀斯特地形，你所在的省、自治区、市有这样的地方吗？