Q: In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.
Article: Five years ago, I was sent to a better middle school. For me, everything there was new and strange. After I had been there for two months, there was an important test in the middle of the term. It covered all my courses. In that test, I didn't get a good grade, but most of my classmates got an A. It made me upset for a long time. I felt everything in the world was changing. I thought my classmates were all better than me. During those days I was very unhappy. One day, my aunt, after talking with my teachers, talked to me. She told me to think about what I had done in the past and what I should do in the future. I was shocked by her words. I thought about what I had done during the past months, and I found I had done nothing to improve my grades. I thought I should work harder. After that, I paid more attention to the teachers' talking in the classes, and I asked my teachers or my classmates when I didn't understand something. I studied very late at night when I met with difficult problems. Most of all, I came to understand the importance of taking notes in class. As a result, I did better in some tests. About three months later, the most important test came at the end of the term. _ From then on, I have tried to do my best when I do something because I know if I want something, I should work hard for it.
Question: Why did the writer fall behind in the new middle school? _
Options: (A) Because the teachers didn't treat him well enough. (B) Because the subjects were becoming more difficult. (C) Because he hated the life in the new school. (D) Because he didn't put his heart into study.
A:
D