求费费逻辑讲义答案～

tracychen36

RT～没有答案，有一题完全不懂....

The presence of microorganisms that produce a toxin cause sweater to turn brownish red,

phenomenon known as a red ride. Sea otters do not feed in areas where clams, their main source of food, have become contaminated with this toxin. According to a proposed explanation of the otter’s behavior, the otters sample the clams in a potential feeding area and can taste any toxin in them.

  Which of the following, if true, would most strongly indicate that the hypothesis described in the last

sentence of the passage of the passage is not correct?

(A) In some of the area where red tides occur, neither clams nor sea otters are indigenous species.

(B) The presence of sea otters in a given area has a significant effect on which other marine

organisms are to be found in that areas.

(C) When seawater in an area unaffected by red tide is artificially dyed brownish red, sea otters do

not feed on the clams in that area.

(D) If the clams in a given areas are contaminated with toxin, sea otters move to other areas in search

of food.

(E) Although very small amounts of the toxin produced during a red tide are not harmful, large doses

can be fatal to animals the size of sea otters.

alohabrian

选C吧。

原文的意思是：
当 red tide发生，出现两件事：1.海水变成brownish. 2. 有toxin出现。

生活在seawater中的clam有两种下场：被染成 brownish,or 被toxin感染。

此时：人们又发觉sea otters不吃clams了，于是就认为sea otters可以辨别 clam身上的toxin。（此处有逻辑缺陷：挑出clam的办法有二：
1.看颜色 2辨别toxin，怎么一定能说 sea otter是通过辨别toxin来sample clams的呢？）

C说，当海水中没有toxin,颜色变brownish red的时候，sea otter还是不吃clam,证明otters不吃clam所以其实是因为颜色变化，sea otter辨识的出哪些clams变红了。

基本逻辑线可以归纳一下：假设factor A和 factor B都可能使Subject做出某种行为C，当某一个condition出现，并同时包含A和B，怎么就一定能判断是因为哪个 factor导致 subject做出行为C？

方法：控制 其中一个factor改变另一个factor,看看结果是否发生。

[此贴子已经被作者于2009-3-13 19:32:33编辑过]

sausau

肯定有答案，而且还是有详细答案！！！