第15练 阅读理解＋任务型阅读＋短文改错
Ⅰ.阅读理解
A
体裁：记叙文 话题：动物世界 词数：330 时间：7′
Tropical fish hobbyists will tell you their tanks are a source of relaxation，but recent research suggests the fish might disagree.
Many American households contain a fish tank，whose average size is less than 10 gallons.Yet a study comparing the behavior of common freshwater fish found that those kept in such small tanks were more aggressive than those in larger ones and were more likely to fight.
“If people kept dogs in these conditions，they'd be put in prison，” said the author，Ronald Oldfield.“In larger tanks，the fish were not in continuous eyesight of each other.They were swimming around，checking everything out rather than beating each other，” he added.“It's something we should think about.”
The study consisted of two experiments.In one，Dr.Oldfield tested the effects of overcrowding by keeping tank size constant (不变) while increasing the number of fish.In the other，he tested environment by placing three fish in tanks of different sizes.He then recorded their behavior at least two hours after feeding，to eliminate (排除)competitive behaviors related to food.While aggression seemed to remain constant regardless of the number of fish in a tank，it dropped off considerably once the fish were placed in a 100gallon tank with several
