Instructions: 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.
Input: Article: Doing homework not only can help children master the knowledge they have learned, but also can train their abilities of finishing the work alone, planning the time and doing the duties. But some children don't like to complete the work. Why? There are some reasons. Some children feel it is very difficult to do their homework, because they can't understand their teacher clearly, and can't follow their teacher's teaching process. Maybe there is something wrong with their _  But some children's intelligence is normal. They are even cleverer, but they don't listen to the teacher carefully. It is hard for them to sit well and pay attention to anything. It needs to carry on the attention centralized training to help the children. Some children love their teacher and then they like the subject. Their interest depends on the teacher who teaches them. So every teacher should be helpful and kind. It can make children love you and the subject you teach. So they can do their homework happily. 
 Question: Doing homework can help children  _  . 
 Options: (A) master the knowledge (B) train their abilities (C) lean new lessons (D) Both A and B
Output:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
D