Prep T1-22

[evangelinewu]

22. (28829-!-item-!-188;#058&003748)

In the late 1980s, the population of sea otters in the North Pacific began to decline. There are two plausible explanations for the decline: predation, possibly by killer whales, or disease. Of these two, disease is the more likely, since a concurrent sharp decline in populations of seals and sea lions is believed to have been caused by disease, and diseases that infect these creatures are likely to be able to infect sea otters also.

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

(A) Killer whales 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 the sea otter population at any North Pacific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.

(C) Along the Pacific coast of North America in the 1980s, 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.

ANS:A

[evangelinewu]

22. (28829-!-item-!-188;#058&003748)

In the late 1980s, the population of sea otters in the North Pacific began to decline. There are two plausible explanations for the decline: predation, possibly by killer whales, or disease. Of these two, disease is the more likely, since a concurrent sharp decline in populations of seals and sea lions is believed to have been caused by disease, and diseases that infect these creatures are likely to be able to infect sea otters also.

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

(A) Killer whales 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 the sea otter population at any North Pacific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.

(C) Along the Pacific coast of North America in the 1980s, 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.

ANS:A

不太瞭解B選項的句意
是說沒有跡象顯示大規模sea otter的遷移是造成他們數量減少的原因嗎?

這題我的思路是：disease造成sea lion等動物死亡...又因為這種disease可能也會影響sea otter....所以disease造成population下降

故A選項：killer whales因為補不到sea lion,轉而尋求其他食物來源，故造成sea otter減少的原因不是disease,是其他predator的捕食，可以weaken上述reasoning(他因否定)
不知道我想的對不對，請大家指教

[dibert8]

應該是吧!

看到 CR 也講究對稱.
弱化 disease: seals and sea lions 生病, sea otters 也會感染相同的病
把 disease 換成 predation => (A) seals and sea lions 被 Killer whales 捕食, sea otters 也會被 Killer whales 捕食 (i.e. predation 造成 sea otters 減少).

(B) sea otters 減少不是因為遷移 (無關的選項囉!)

[Huang Hsin-Yi]

22. (28829-!-item-!-188;#058&003748)


故A選項：killer whales因為補不到sea lion,轉而尋求其他食物來源，故造成sea otter減少的原因不是disease,是其他predator的捕食，可以weaken上述reasoning(他因否定)
不知道我想的對不對，請大家指教

你講的很對

[daskooler]

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

請問為什麼C這個選項不行呢

[sorryself]

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

請問為什麼C這個選項不行呢

這只說明了一個事實，
就是"In the late 1980s, the population of sea otters in the North Pacific began to decline."換句話說而已，
沒有weaken或support的效果。