A. the current levels of water in the river b.the type of pollen in cores from a nondrought period b. the type of pollen in cores from a nondrought period c.the composition of microscopic charcoal released during natural fires c. the composition of microscopic charcoal released during natural fires d.the quantities of sediments in cores from the delta during a nondrought period d. the quantities of sediments in cores from the delta during a nondrought period
