reduced evaporation.

　　Another problematic method is to reconstruct former

　　climates on the basis of pollen profiles. The type of vege-

　　tation in a specific region is determined by identifying

　　（45） and counting the various pollen grains found there.

　　Although the relationship between vegetation and

　　climate is not as direct as the relationship between

　　climate and lake levels， the method often works well in

　　the temperate zones. In arid and semiarid regions in

　　（50） which there is not much vegetation， however， small

　　changes in one or a few plant types can change the

　　picture dramatically， making accurate correlations

　　between neighboring areas difficult to obtain.

　　1. Which of the following statements about the difference between marine and continental sedimentation is supported by information in the passage？

　　（A） Data provided by dating marine sedimentation is more consistent with researchers' findings in other disciplines than is data provided by dating continental sedimentation.

　　（B） It is easier to estimate the age of a layer in a sequence of continental sedimentation than it is to estimate the age of a layer in a sequence of marine sedimentation.

　　（C） Marine sedimentation is much less widespread than continental sedimentation.

　　（D） Researchers are more often forced to rely on extrapolation when dating a layer of marine sedimentation than when dating a layer of continental sedimentation.

　　（E） Marine sedimentation is much more continuous than is continental sedimentation.

　　2. Which of the following statements best describes the organization of the passage as a whole？

　　（A） The author describes a method for determining past climatic conditions and then offers specific examples of situations in which it has been used.

　　（B） The author discusses the method of dating marine and continental sequences and then explains how dating is more difficult with lake levels than with pollen profiles.

　　（C） The author describes the common requirements of methods for determining past climatic conditions and then discusses examples of such methods.

　　（D） The author describes various ways of choosing a material for determining past climatic conditions and then discusses how two such methods have yielded contradictory data.

　　（E） The author describes how methods for determining past climatic conditions were first developed and then describes two of the earliest known methods.