When I don't understand the math problem, Tom always helps me with it , he is my walking ________.
问题描述：
When I don't understand the math problem, Tom always helps me with it , he is my walking ________.
When I don’t understand the math problem,
Tom always helps me with it , he is my walking ________.
A. directorB dialogue C. dictionary D. duty
答
C.dictionary
walking dictionary 活字典