Thanks to the vivid , the speaker made the abstract concept accessible to all the audience

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A. inflation
B. interference
C. illiteracy
(答案→)D. illustration
解析：词义辨析。inflation 通货膨胀；interference 干扰，冲突；illiteracy 文盲，无知；illustration说明，图解。句意：由于这生动的图解，演讲者让所有观众接受了这些抽象的概念。故选D。