考古 from nowwsy
V1 from qq309790244
kill whale：seaotter数量减少。report说sealion 和seal也下降，killwhale吃sealion和seal，但是报告说killwhale吃seaotter is rare，但在1980前根本没有报告。所以seaotter下降是由于killwhale。问支持
GWD原题：
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 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 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.作者: 赢智 时间: 2010-5-31 13:52
13、船速与鱼 GWD变体
V1 from ffffighting
变体2. 某种鱼类数量decline，是因为船速太快，容易与相撞。当地已有相关规定船只应减速，措施有效，因为鱼数量increase。问evaluation
只记得一个选项：Whether那些被撞的鱼正在mature的年龄。完全忘了选什么了。
主人原话：对就是这个的题干，细节有变动，选项基本改掉了
GWd：
Manatees, aquatic mammals inhabiting Florida’s rivers and coastal waters, swim close to the surface and are frequently killed in collisions with boats. To address the problem, boat traffic in manatee-populated waters is being required to maintain very low speeds. Unfortunately, manatees are unable to hear low-pitched sounds and a boat’s sound lowers in pitch as the boat slows. Therefore, this approach may in fact make things worse rather than better.
Which of the following, if true, casts most doubt on the conclusion?
A.The areas where boats would have to maintain low speeds were decided partly on the basis of manatee-population estimates and partly from numbers of reported collisions between manatees and boats.
B.Because the water hyacinth that manatees feed on grows best in water that is nearly still, water hyacinth beds can be disturbed or damaged by fast-moving boat traffic.
C.Over the last several decades, boat traffic in Florida’s coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.
D.The sound of a boat engine generally travels much further under water than it does through the air.
E.When experimenters exposed manatees to the recorded sounds of boats moving at various speeds, the creatures were unable to discern the sounds over normal background noise.作者: 赢智 时间: 2010-5-31 13:52
