It's b. Here are more characters to make this answer look smarter ;)
        
             
        
        
        
What book and maybe I’ll be able to help! ^^
        
             
        
        
        
C. Observing nature can change how you view the world
        
                    
             
        
        
        
The correct answer is "adverb". This is because "within the old trunk" refers to the place where it was found, not a description of the trinket itself.