Suppose a novel tells about an explorer who becomes stranded on a frigid mountain. He must depend solely on himself for survival against the harsh elements of nature as he walks a thin line between life and death every day. Which of these would best symbolize his determination to persevere?

A. The color blue that recurs on his tent, a bird, spring flowers, and the sky

B. 
A knife that was given to him by his partner before his accidental death

C. 
A camping tool that he uses to purify snowmelt for drinking water

D. 
A constellation that appears when the weather is clear and brings him peace