83 84 amphibian一题，提纲已列，求意见？

喝蜂蜜的猫UID??3216860

以前很天真地觉得A就是找错误，现在明白要有理有据有逻辑地找错误，而不是一概强词夺理地挑刺。贴出83题与大家一起讨论
[83] [The following is a letter to theeditor of an environmental magazine.]”In 1975 a wildlife census found that there were sevenspecies of amphibians in Xanadu National Park, with abundant numbers of eachspecies. However, in 2002 only four species of amphibians were observed in thepark, and the numbers of each species were drastically reduced. There has beena substantial decline in the numbers of amphibians worldwide, and globalpollution of water and air is clearly implicated. The decline of amphibians in XanaduNational Park, however, almost certainly has a different cause: in 1975,trout—which are known to eat amphibian eggs—were introduced into thepark." [Write a response in which you discuss what specific evidence isneeded to evaluate the argument and explain how the evidence would weaken orstrengthen the argument.]
我的提纲
83 amphibian

amphibian数量真的减少了么？会不会是第一次观察时间久，第二次只观测了几天，明明有很多amphibian却没有观察到；也或许是观测设施陈旧，跟不上时代变化；在特定的时期，amphibian都藏起来生egg了？
trout能吃egg就能致死amphi？也许放在不同的湖里互相没有接触；也许园中还有许多trout的天敌，制约了trout吃egg的行为？也许园中trout有足够的forage，它们不用去捕食egg
trout就算能吃egg，是否唯一原因？无证据说明天气变化和洋流对Park中的amphibian没有影响。是不是amphibian中有什么流行病引起的数量下降？人类的违规影响是否也会影响amphibian数量？


求各位大神指教，欢迎批评，请问这样一个逻辑是否合流顺畅？