95.
Which of the following most logically completes the passage?
Using new detection techniques, researchers have found trace amounts of various medicinal substances in lakes and rivers. Taken in large quantities, these substances could have serious health effects, but they are present in quantities far too low to cause any physiological response in people who drink the water or bathe in it. Nevertheless, medical experts contend that eliminating these trace amounts from the water will have public health benefits, since __________.
A. some of the medicinal substances found in lakes and rivers are harmless to humans even if taken in large quantities
B. some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there
C. people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed
D. most medicinal substances that reach lakes or rivers rapidly break down into harmless substances
E. disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them
100.
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these other species were increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.
Which of the following would it be most important to ascertain in evaluating the argument?
A. Whether populations of the other species on which deer tick larvae feed are found only in areas also inhabited by white-footed mice
B. Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on
C. Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice
D. Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed
E. Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans
Ａ：是否白腿老鼠和其他种类的宿主老鼠住在一样的地方。因为题干已经说了If the population of these other species were increased, more of the larvae would be feeding on uninfected hosts，因此这个逻辑部分已经被填充好了，不管这几个宿主是否住在一样的地方，只要其他的数量增加了，就会有更多的幼虫寄生在未感染的宿主上～
讲的不太清楚，还请多多指教～作者: pangpangshin 时间: 2011-1-14 20:52
