First, I selected option A because it is explicitly mentioned in the text, which confused me. After reading the question several times, I realized the correct answer is C, because it asks for "carefully examining the possible causes." My problem was that I misinterpreted a detail.I didn’t understand the question clearly and was influenced by the first option, since it was reflected in the text. So, I will practice several times to avoid this kind of problem, because if I don’t understand the question, I won’t choose the correct answer.