People diet to look more attractive．Fish diet to avoid being beaten up，thrown out of their social group，and getting eaten as a result．That is the fascinating conclusion of the latest research into fish behavior by a team of Australian scientists．
The research team have discovered that subordinate(低一等的) fish voluntarily diet to avoid challenging their larger petitors．In studying gobies we noticed that only the largest two individuals，a male and female，had breeding（繁殖）rights within the group， explains Marian Wong．All other group members are nonbreeding females，each being 5-10% smaller than its next largest petitor．We wanted to find out how they maintain this precise size separation．
The reason for the size difference was easy to see．Once a subordinate fish grows to within 5-10% of the size of its larger petitor，it causes a fight which usually ends in the smaller goby being driven away from the group．More often than not，the evicted fish is then eaten up．
It appeared that the smaller fish were keeping themselves small in order to avoid challenging the boss fish．Whether they did so voluntarily，by restraining how much they ate，was not clear．The research team decided to do an experiment．They tried to fatten up some of the subordinate gobies to see what happened．To their surprise，the gobies simply refused the extra food they were offered，clearly preferring to remain small and avoid fights，over having a feast．
The discovery challenges the traditional scientific view of how boss individuals keep their position in a group．Previously it was thought that large individuals simply used their weight and size to threaten their subordinates and take more of the food for themselves，so keeping their petitors small．
While the habits of gobies may seem a little mysterious，Dr．Wong explains that understanding the relationships between boss and subordinate animals is important to understand how hierarchical（等级的）societies remain stable．
The research has proved the fact that voluntary dieting is a habit far from exclusive to humans．As yet，we lack a plete understanding of how widespread the voluntary reduction of food intake is in nature， the researchers ment．Data on human dieting suggests that，while humans generally diet to improve health or increase attractiveness，rarely does it improve long-term health and males regularly prefer females that are fatter than the females' own ideal．
【小题1】When a goby grows to within 5-10% of the size of its larger petitor，it ．A．leaves the group itselfB．has breeding rights C．eats its petitorD．faces danger【小题2】The underlined words the evicted fish in Paragraph 3 refer to ．A．the fish beaten up B．the fish driven awayC．the fish found outD．the fish fattened up【小题3】The experiment showed that the smaller fish ．A．fought over a feastB．preferred some extra foodC．challenged the boss fishD．went on diet willingly【小题4】What is the text mainly about? A．Fish dieting and human dieting．B．Dieting and health．C．Human dieting．D．Fish dieting．D
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(答案→)D
解析：全文说明了最新的研究成果——鱼类为什么节食。文章先以人为对比，引出鱼类节食这个话题，在随后的几个段落里，作者要对这个发现进行具体说明。
【小题1】推理判断题。从第二段each being 5-10% smaller than its next largest petitor可得知如果身体大小超过权威的规定范围，会有被殴打、驱逐最后被吃掉的危险。选D
【小题2】猜测词义题。从本段前文可知，体积超标的鱼会被赶出鱼群。接着说到，不仅如此，这些鱼往往会被吃掉。这些鱼一定是指被驱逐的鱼。选B
【小题3】事实细节题。从第四段中的试验和句子：To their surprise，the gobies simply refused the extra food they were offered，clearly preferring to remain small and avoid fights，over having a feast．可得知这些鱼是自愿节食。故选D
【小题4】主旨大意题。从文章的第一段的内容Fish diet to avoid being beaten up，thrown out of their social group，and getting eaten as a result．和文章通篇可知都是围绕鱼的节食来叙述。故选 D。