题目

阅读理解 A pretty face is never forgotten. Do you believe so? Butmaybe it is untrue! Psychologists believe beautiful people are less likely tobe recognized. A new study suggests that attractiveness can actually preventthe recognition of faces, unless a pretty face has particularly distinctivefeatures, such as Angelina Jolie's. German psychologists think the recognition of pretty facesis distorted (扭曲)by emotions. Researchers Holger Wiese, Carolin Altmann and Stefan Schweinbergerat the University of Jena, Germany, discovered in a study that photos ofunattractive people were more easily 下图是检验某无色气体A是SO2和CO2的混合气体的装置图，按要求回答下列问题。  (1)B中加入的试剂是________，作用是____________________________________________。 (2)C中加入的试剂是__________，作用是_______________________________________。 (3)D中加入的试剂是________，作用是_________________________________________。 (4)实验时，C中应观察到的现象是_______________________________________。