Please Post the story So I can answer your question and put who character S is.
The answer would be A. because the story is not about the glass of milk.
The line that states, "courage is a man with a gun in his hand." It is a metaphor because Lee is not comparing courage to a man with a gun with "like" or "as." Instead, she uses "is", as if she is enforcing the fact that courage IS a man with a gun. That kind of bluntness is only in a metaphor, as the author gives no room for debate.
I believe it's 'Come on, Sammy, pedal this bike faster!'