Teacher:You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. 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.
Teacher: Now, understand the problem? Solve this instance: Rheumatoid arthritis is an autoimmune disease that affects the joints. Which of these events causes the symptoms of this disease?
(A) The body's immune system attacks specific tissues. (B) The cells of the immune system begin to grow rapidly. (C) The body's immune system fails to fight off infections. (D) The cells of the immune system are absorbed by antigens.
Student:
A