请教关于weaken的问题

shineyang

Premiserinking milk causes cancer.
Premise:In North American, people drink a lot of milk.
Conclusion:Therefore, there is a high frequency of cancer in NA.
谁能帮忙分析一下这个weaken的原因啊？谢谢谢谢啦！

sdcar2010

1) In North American, people exercise regularly. Study shows that exercising regularly has anti-cancer effect.
2) Study shows that people in NA have  a special anticancer gene.
3) Study shows that drinking 3 cups of milk daily causes cancer, but drinking 1 cup of milk daily does not cause cancer. In NA, people drink one cup of milk daily.

eynl12345

我做题时喜欢把这种题目归为预测型。
我的思路就是 寻找反作用因素 或者 质疑前提的正作用不够
LS的1，2就是在找反作用因素，3就是质疑前提的正作用不够。