The passage is sequentially organized in which of the following ways?

• A. Define a problem; explain the sources of the problem; offer a solution to the problem
• B. Pose a question; offer an answer to the question; offer an alternative answer to the question
• C. Introduce a mystery; offer an explanation for the mystery; provide an alternative explanation for the mystery
• D. Introduce an enigma; explain the reasons for the enigma; discuss the inevitability of the enigma