标题: og12- cr62 没搜到 [打印本页] 作者: 好运9月9 时间: 2010-8-15 12:13 标题: og12- cr62 没搜到 When there is less rainfall than normal, the water level of Australian rivers falls and the rivers fl ow more slowly. Because algae whose habitat is river water grow best in slow-moving water, the amount of algae per unit of water generally increases when there has been little rain. By contrast, however, following a period of extreme drought, algae levels are low even in very slow-moving river water.
Which of the following, if true, does most to explain the contrast described above?
(A) During periods of extreme drought, the populations of some of the species that feed on algae tend to fall.
(B) The more slowly water moves, the more conducive its temperature is to the growth of algae.
(C) When algae populations reach very high levels, conditions within the river can become toxic for some of the other species that normally live there.
(D) Australian rivers dry up completely for short intervals in periods of extreme drought.
(E) Except during periods of extreme drought, algae levels tend to be higher in rivers in which the fl ow has been controlled by damming than in rivers that fl ow freely.
吃藻类的动物少了 ，可能藻类数量会上升呢~ 这就不能解释 极度干旱后 藻类数量低了作者: 好运9月9 时间: 2010-8-15 15:07
哦！ 对对 以为是藻类的食物下降了呢。。 感谢作者: dengdengtu 时间: 2010-8-24 22:48
没弄明白D啊······求解~作者: 歆欣12388 时间: 2010-9-30 20:07
algae levels are low even in very slow-moving river water,还是在water环境中的呀，怎么D选项就说dry up了algae 就没了呢？不懂作者: syr1988 时间: 2010-10-30 05:46
同问！！作者: 三零年代 时间: 2010-10-30 09:31
(D) Australian rivers dry up completely for short intervals in periods of extreme drought.
澳大利亚河流完全干涸，在嫉妒干旱的一个很短的时间段内。 首先用排除法: A 与结论刚好想法 B 水流动越慢，越有利于海藻生存。-- 无关 C 海藻越多，毒越多，不利于其他物种生存 -- 无关 D 澳大利亚河流完全干涸，在极度干旱的一个很短的时间段内。（海藻生存需要水）有点沾边，先留着 E 无关，前半句就直接排除了。 所以选D. 其他更错了。作者: GWinner 时间: 2012-3-5 09:25
好吧feed on是“以..为食”的意思...晕了> <~ 看来只能用排除法了.....