V. Discourse Structure:         Temperatures in cities have been reported to reach record high. When summer is approaching, city dwellers flee to somewhere else to beat the heat and keep off the blazing sun. A question, thus, pops up: why are cities are hotter? _41_ People, buildings, the machinery, and less reflectiveness contribute to the higher temperatures of cities. However, based on a recent study, _42_ According to NASA satellite data, a number of various factors have a big impact on the UHI effect. They are evaporation, heat created by humans and their structures, heat stored by cities, differences in land surface types and disparities in convection. The researchers further determined that the last two factors played a decisive role in the local climate. On the one hand, humid areas of cities are less efficient at dispersing heat and _43_. Interestingly enough, in dry areas, the opposite takes place. So recognizable is the convection difference in dry regions that these cities over there experience no UHI effect.        Actually, the UHI effect is more than just an annoyance for city dwellers, which worsens such problems as heat stroke or heat exhaustion. _44_ One solution looks acceptable but does not help that much: to reduce the heat from air conditioners and other machinery. Instead, how to increase the reflectiveness of the city is a preferable solution. This is a time-honored proof: the reflectiveness of light colors decreases the heat during the day and at night. White roofs are also worth serious consideration. _45_ Because tall buildings are being planted in cities throughout the world one after another, new technology and public awareness may help address the UHI effect. (AB) the local climate may be the primary factor behind the UHI effect. (AC) Fortunately, some solutions to the UHI effect have been put forward to lower some of that heat. (AD) It is the “urban heat island” (UHI) effect that makes cities with big populations warmer during the day and at night. (AE) They not only cut down on energy use but also balance out the heat absorbed by these buildings. (BC) on the other hand, the dense vegetation of a rural area steps up the efficiency of the convection process(BD) A city, deprived of human activities, is bound to be UHI-free.
【題組】41.