The answer would be your third choice. Visualize means to see something so that is your answer
I believe it is B as he used such soft words for the imagery as he imagined about him being older.
Answer:
B. Idea
Bold - (of a person, action, or idea) showing an ability to take risks; confident and courageous.
A history or background, Especially One created for a fictional character in a motion, picture, or television program.
