Answer: It would be D.
Explanation: they are synonyms 
 
        
             
        
        
        
Answer:
According to Rowling, Failures:
Give an inner security that  had never attained by passing examinations. Teach things about ourselves that  could have learned no other way. 
Let us discover weI had a strong will, and more discipline than  had suspected
She discusses these based on her own experiences.