A.I. Explanation:

Option 1: "to persuade the reader that cities need to prepare for increased populations."

Explanation: The text emphasizes the necessity for cities to prepare for a rising population, indicating that increased demand for services will require proactive measures. The phrase 'it is important for cities to prepare' directly supports this purpose, aligning with the overall theme of urban planning and infrastructure investment.

Option 2: "to make it clear that cities want to be efficient and attractive places for anybody who wants to come in."

Explanation: While the text mentions that cities should be efficient and attractive, it does not focus on the desire of cities to attract newcomers. Instead, the main purpose is about preparation for population growth, making this option too broad and not aligned with the text's primary message.

Option 3: "to highlight the amount of green space available."

Explanation: Although the text discusses green space in Songdo, it is not the main focus. The mention of green space serves as an example of how cities can prepare for increased populations, rather than being the central purpose of the text.

Option 4: "to show the importance of roof gardens in the event of stormy weather."

Explanation: The text briefly mentions roof gardens as a feature of Songdo, but it does not specifically emphasize their importance in stormy weather. This option misrepresents the text's main purpose, which is about overall city preparation for population growth rather than focusing on a single aspect like roof gardens.