讨论关于40年前黄腿山蛙数量下降的三种解释。

Refute the three explanations mentioned in reading passage.
1. The trout was introduced 100 years ago, however the decline happened 40 years ago. The time does not match.
2. Rainfall tends to wash the pesticides to lower and farther places. However, frogs lived in areas with higher altitude than that of farms using pesticides.
3. Yellow-legged mountain frogs can produce some antibodies within their bodies, so that they can resist to the infection of fungal disease.
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Demonstrate three theories to explain why the number of yellow-legged mountain frogs declined 40 years ago.
1. A kind of fish, the trout, was introduced to this area and the trout ate tadpoles of the frogs.
2. The use of pesticides contaminated the habitat.
3. The frogs there were infected by a fungal disease.