GRE阅读:in response to到底是问个啥?

Witnesses to a meteor in Australia in 1978 claimed to have heard strange noises as it streaked overhead. Yet, given that the meteor was 30 kilometers up, if these sounds had come directly from the meteor, people on the ground could not have heard them until almost a minute after the meteor had disappeared.Physicist Colin Keay hypothesized that the light given off by a meteor’s trail must be accompanied by invisible electromagnetic radiation in the form of very low frequency (VLF) radio waves.Such waves, which travel at the speed of light, would reach the observer when the meteor itself came into view.

Biologists know that some marine algae can create clouds by producing the gas dimethyl sulphide (DMS), which reacts with oxygen in air above the sea to form solid particles. These particles provide a surface on which water vapor can condense to form clouds. Lovelock contends that this process is part of a global climate-control system; according to Lovelock, Earth acts like a super organism, with all its biological and physical systems cooperating to keep ithealthy. He hypothesizedthat warmer conditions increase algal activity and DMS output, seeding more clouds, which cool the planet by blocking out the Sun. Then, as the climate cools, algal activity and DMS levels decrease and the cycle continues.In response tobiologists who question how organisms presumably working for their own selfish ends could have evolved to behave in a way that benefits the planet, Lovelock points out that DMS production benefits not only the planet but the organisms as well: cooling benefits the algae, which remain at the ocean surface, because it allows the cooled upper layers of the ocean to sink, and then the circulating water carries nutrients upward from the depths below. Algae may also benefit from nitrogen raining down from clouds they have helped to form.

According to the prevailing view, Homo erectus, an ancestor of Homo sapiens, lacked the intellectual and technological sophistication to have achieved controlled use of fire; that had to wait for the emergence of H. sapiens 40,000 years ago. However, recent evidence seriously undermines this view. At two sites in Kenya, many small,lens-shaped patchesof discolored earth were uncovered along with bones and stone tools of H. erectus. Analysis showed that the patches, which, like the tools and bones, dated from 1.6 million years ago, were almost certainly the result of deliberately built fires, since those fires were evidently much hotter than typical naturally occurring bush fires. The size of the patches rules out lightning strikes, which could have explained the fires’ high temperatures. Furthermore, the fires were fed by a mixture of grasses and woods that strongly suggests deliberately collected fuel. In addition, many of H. erectus’ tools were made of basalt or quartz, stones which, when exposed to the intense heat near a campfire, form characteristic dimples on their surface. A recent study found that such dimples never appear on tools dating earlier than 1.6 million years ago but do consistently appear on later tools.3.The fact that “many of H. erectus’ __tools were made of basalt or quartz” is relevant to the argument of the passage for which of the following reasons?

A. No tools made from these stones have been found in sites associated with H. sapiens.

B. These stones must have been deliberately collected for tool use.

C. These stones rarely appear in sites dating later than 40,000 years ago.

D. The tools formed from these stones could not have been formed without the use of intense heat.

E.These stones develop certain characteristicsin response tohigh temperatures.

Since 1989, the size of the Porcupine caribou herd in Alaska has undergone a steady downward trend, declining at a rate of 3 to 4 percent a year. Just why this is happening is not clear. Biologists have not observed marked changes in birthrate or calf survival, nor has there been an increase in the number of predators; consequently, some biologists have turned their attention to global warming.The rise in spring temperatures may be changing conditions along the migration route in ways that make life difficult for caribou.For example, prematurely soggy snow might force the animals up onto windswept ridge tops, where they are easier prey for wolves.1.The passage suggests which of the following about the migration of the Porcupine caribou herd in Alaska?

A. Prior to 1989, the herd had not been preyed upon by wolves during migration.

B. Prior to the rise in spring temperatures, the herd typically did not travel along windswept ridge tops while migrating.

C. The herd has altered its migration patternin response topredation.

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