My is the pronoun. 
It is possessive (because it’s talking about their books)
It is demonstrative (because it is talking about where the books are)
        
             
        
        
        
The dependent variable is that she bites her nails. Being nervous is an independent variable due to that it doesn't depend on anything said. However, in order for her to bite her nails, she has to be nervous as stated.
        
                    
             
        
        
        
The type of exposition that is illustrated in this paragraph is illustration and example because in the first idea of the paragraph the picture of the topic is described by features and characteristics to give the reader that idea of large amount of unhealthy edible elements people eat per meal, and in the second idea of it there is an example that just looking at the menu, people may recognize the health problems eating these plates brings.