GRE Reading Comprehension: PPO-GRE阅读PPO - DUBD4J18BB12WKZKR

It can be inferred from the passage that by setting out new cards when replacing the dish of sugar water with an empty one, Frisch A. was able to record accurately any changes in color that resulted from spills or drops B. could subtly alter the color of the card on which the sugar water was placed in each iteration of the experiment C. introduced new clues relevant to finding the sugar water's location D. succeeded in proving that bees see in only a limited spectrum of color E. was able to rule out the possibility that the bees had somehow marked the blue card in previous trials