gre考试阅读真题解析(B)_GRE阅读

gre考试阅读真题解析(B)

　　 some of the phenomena measured by digital multi-spectral images in remote sensing

　　 some of the practical uses of regional geologic maps

　　 the kinds of problems that are difficult to solve solely through conventional methods of geologic mapping

　　 the specific limitations of the Landsat multi-spectral scanner

　　23. The passage suggests which of the following about the conventional methods mentioned in line 29?

　　 They consist primarily of field surveys and laboratory measurements.

　　 They are not useful in providing information necessary for reconstructing geologic evolution.

　　 They have rarely been used by geologists since 1972.

　　 They are used primarily to gather compositional information about geologic features.

　　 They are limited primarily because of difficulties involved in interpreting film images.

　　Although the development of new infrastructure is usually determined by governmental planning, sometimes this development can be planned more flexibly and realistically by private investors who anticipate profit from the collection of user fees. Such profits can contribute to the financing of more infrastructure if demand proves great enough, whereas the reluctance of developers to invest in such projects can signal that additional infrastructure is not needed. During the economic boom of the 1980s, for example, the state of Virginia authorized private developers to build a $300 million toll road . These developers obtained the needed right-of-way from property owners, but by 1993 they still had not raised the necessary financing. The unwillingness of investors to finance this project does not negate the viability of privately financed roads; rather, it illustrates a virtue of private financing. If a road appears unlikely to attract enough future traffic to pay for the road, then it should not be built.