4. Which of the following would be the most likely topic for a paragraph that logically continues the passage?
(A) The kinds of plants normally found in arid regions
(B) The effect of variation in lake levels on pollen distribution
(C) The material best suited to preserving signals of climatic changes
(D) Other criteria invoked by paleoclimatologists when choosing a method to determine past climatic
conditions
(E) A third method for investigating past climatic conditions

5. The author discusses lake levels in the southwestern United States in order to
(A) illustrate the mechanics of the relationship between lake level, evaporation, and precipitation
(B) provide an example of the uncertainty involved in interpreting lake levels
(C) prove that there are not enough ancient lakes with which to make accurate correlations
(D) explain the effects of increased rates of evaporation on levels of precipitation
(E) suggest that snow-line elevations are invariably more accurate than lake levels in determining rates of precipitation at various points in the past

6. It can be inferred from the passage that an environmental signal found in geological material would not be useful to paleoclimatologists if it
(A) had to be interpreted by modern chemical means
(B) reflected a change in climate rather than a long- term climatic condition
(C) was incorporated into a material as the material was forming
(D) also reflected subsequent environmental changes
(E) was contained in a continental rather than a marine sequence