the following appeared in a brenton newspaper.

　　"the brenton power plant draws water from scott's river for its cooling system and releases the warmed water back into the river. the town council recommends that the plant install a more efficient cooling system that uses less water, claiming it will be more environmentally sound. however, in uptown, where the new system is used, a study found that the complex network of pipes in the new system tends to accumulate algae¹. the build up of algae can be avoided by scrubbing the pipes, which is costly², or by adding an herbicide to the water in the pipes to prevent algae accumulation. but water containing the herbicide cannot be released back into the river and it is known that low water levels can harm river ecosystems³ accustomed to higher levels. therefore, brenton power plant should continue to use the old cooling system exclusively."

　　the following appeared in an editorial in the seatown newspaper.

　　"seatown has a large port exclusively for fishing boats, whose owners pay fees for the upkeep of the docks and for facilities for cleaning engines and repairing nets. in recent years, declining fish populations have decreased fishing revenue and forced many owners to stop fishing altogether. as a result, the port has a high vacancy⁴ rate and port managers are considering allowing pleasure boats, including cruise ships and other large vessels⁵, to use the port in order to increase revenue. but allowing pleasure boats into the port would be a mistake, because the fishing boats would be forced out of the port. we should preserve the port for the fishing fleet, which, unlike pleasure boats, contributes to the prosperity of seatown."

　　the following editorial appeared in a newspaper in the country of solaria.

　　"the eliot valley region was primarily agricultural twenty years ago. in the past twenty years, however, many computer-chip manufacturers have opened factories there. a recent study found that water pollution in the region was worse than in any other region in the country. moreover, the computer-chip factories, which use large quantities of water to manufacture the chips, are probably responsible for the low levels of water in the region's lakes and reservoirs. therefore, if the region's computer-chip makers⁶ had limits placed on the amount of water they could use, water quality would improve."

　　the following appeared in a health newsletter.

　　"according to a recent study, people with many social ties report catching⁷ colds less often than do people with few social ties. consequently, researchers conclude that having an active social life probably helps strengthen the immune system. the researchers note that catching a cold—one of a family of highly contagious⁸ viruses—gives the cold-sufferer temporary immunity⁹ to that virus in the future, but not to the many other related viruses. merely being exposed to a new cold virus, however, is not enough for a person to catch a cold, since a strong immune system can successfully fight off some new viruses. thus, in order to prevent catching a cold, people should strengthen their immune systems by becoming more active socially."

　　one kind of brain-scanning device is used by doctors to monitor normal as well as abnormal activity in a patient's brain. the device provides precise measurements of blood flow in the brain, a known indicator¹⁰ of how the brain is working. unfortunately, the device requires patients to remain completely still with their heads in the scanning machine, which makes a very loud noise. under these uncomfortable conditions, it is doubtful that doctors can get accurate measurements. a new head-mounted device that measures eye movements rather than blood flow and allows patients to move around will undoubtedly¹¹ provide better brain measurements. thus, the new head-mounted device should replace the older device at all hospitals and research institutions.

　　blue city highway had always been notorious for its tight curves and poor roadway visibility, and the accident rate there was generally very high. last year the highway was redesigned to broaden the curves and improve roadway visibility. drivers report that they now feel much safer driving on the highway and that the redesign has been a big improvement. but the number of accidents on the highway has not been significantly lower in the six months since the redesign than it was in the six months before the redesign. therefore, the redesign clearly did not improve the curves and roadway visibility enough to make a difference.