[問題]GWD8-Q3

[mills]

In the late 1980's, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline - increased predation by killer whales or disease - disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whale in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.

B. There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980's.

C. Along the Pacific coast of North America in the 1980's, sea otters were absent from many locations where they had been relatively common in former times.

D. Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters' main food source.

E. The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.

The answer is A.

請問有誰可以幫忙解釋一下這一題嗎?
我實在是看不懂題目本身的reasoning耶
所以也完全不知道該如何weaken
謝謝囉

[fiona]

[size=18]In the late 1980's, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline - increased predation by killer whales or disease - disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whale in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.

B. There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980's.

C. Along the Pacific coast of North America in the 1980's, sea otters were absent from many locations where they had been relatively common in former times.

D. Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters' main food source.

E. The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.[/size]
The answer is A.

請問有誰可以幫忙解釋一下這一題嗎?
我實在是看不懂題目本身的reasoning耶
所以也完全不知道該如何weaken
謝謝囉

題目先敘述一個現象-sea otters 數量減少
在做推論-減少的原因可能是獵食者或疾病 疾病比較有可能
該推論的原因-seals and sea lions 都因某種污染相關的病而掛點 估計也傳染散播給了otters 而且殺人鯨(獵食者)數量並沒有大幅變動

要WEAKEN 就是要找出其實還是殺人鯨吃了這些OTTERS 而不是傳染病的關係
A選項就給了個很好的理由 因為殺人鯨沒有SEALS跟SEA LIONS可吃 所以多吃了OTTERS

有錯誤請指正喔~~

[hccill]

沒有錯!沒有錯!好的很!哈哈...

[jungtsu]

看了大家的解釋我可以理解答案了
可是還是對題目的推論不太明白
為什麼說Seal 跟Sea Lion是因為疾病死亡，且這個疾病可能傳給Otter，然後Whale的數量又不變,就可以推論出因為疾病造成otter死亡?

[jungtsu]

有人可以幫我解答一下嗎
實在不太懂 :(
謝謝 !!

[Austing]

這一句是重點
After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.
disease-->seals and sea lions減少 還有otters可能減少

證據:殺人黥（會吃seals&lions)數量沒改變

所以推論是疾病造成死亡 rather than predation
A:Killer whale in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.殺人黥數量沒改變是因為她有別的食物可以吃並不能拿來當作證據
個人意見:這題不殺 我覺得他沒有很WEAKEN的感覺 其他選項都可以馬上殺

有錯請指教~~

[kaijen]

作者推斷是疾病而非獵食者造成水瀨減少是因 海豹海獅也因疾病而減少了而該疾病可能傳染給水瀨且獵食者數量並未增加
因為若為獵食者造成水瀨減少 獵食者數量應該會增加才是 結論:疾病為主因
(A)weaken疾病為主因 因為殺人鯨會因海豹海獅來源減少 而獵食其他動物 否定疾病為水賴減少的原因