单项选择题

The passage suggests that which of the following would be true if volcanic eruptions did not take place

A．The environment would likely contain fewer non-biodegradable pollutants, due to lesser quantities of sulfurous gases and ash clouds.
B．Greenhouse gas effects on rising global temperatures would likely be somewhat less worrisome than those postulated by scientists today.
C．Acid rain produced by heavy industry would likely be more of a problem than it currently is, given the tendency of volcanic eruptions to hasten atmospheric cycles.
D．Global warming effects caused by human activities would be far more substantial than they are today if volcanic cooling effects ceased to take place.
E． The environment would likely be cooler, for the atmosphere would contain fewer sulfurous gases and ash clouds.

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单项选择题

Which of the following discoveries would likely have an effect upon the views of scientists similar to that of the explosion of El Chico

A．The history of wildfires in North America demonstrates that controlled blazes have a positive effect on the environment, on the whole.
B．The capability of certain metal alloys to withstand great heat proves greater than that of another, confirming metallurgists' suspicions.
C．The study of seismological data proves that existing safety standards in construction will likely prove insufficient in the future.
D．One cigarette brand is found to cause fewer cases of cancer than another brand, disproving the notion that the first brand's contents are more carcinogenic.
E． Ideas concerning the causes of schizophrenia are complicated by the discovery of a rare new psychotic condition whose symptoms defy explanation.

单项选择题

According to the passage, scientists have decided that sulfur aerosols from volcanic eruptions affect global temperatures to a greater extent than ash clouds because

A．the greenhouse gas effect produced by human activities tends to have a much greater environmental effect than that of volcanic explosions
B．clouds of sulfur-rich gases tend to achieve greater heights in the stratosphere than do ash clouds
C．a particular explosion producing high sulfur and little ash had a greater environmental effect than the converse
D．the burning of fossil fuels tends to exacerbate the effects of sulfurous aerosols, but not those of ash clouds
E． global warming effects tend to minimize the impact of ash clouds, but not those of sulfurous aerosols