When many of the guests stayed late into the evening
        
             
        
        
        
I would say C. at ten o'clock; modifies came. Adverb phrase always involves when, where, or how. In this sentence, you could ask when did the truck came? Then you adverb phrase would it came at ten o'clock.
I hope this helps!<span />
        
                    
             
        
        
        
In the characters actions or instead of the idea of their magical actions, you can find the theme, or lesson when a certain problem is solved or unsolved.