Which of the following is a method for collecting official statistics?

The correct answer is registration of births, as it falls under the category of official statistics. Official statistics are quantitative data that are collected by government agencies or official bodies, and they typically include information that is systematically gathered and recorded. The registration of births is a formal and organized method through which data about births is collected, and this data is then used for various purposes, such as demographic analysis and public policy planning.

In contrast, interviews with social workers and focus groups with community leaders involve qualitative methods of data collection, focusing on personal narratives, opinions, and experiences. These methods provide in-depth insights but do not yield official statistics. Additionally, naturalistic observations and recordings are observational methods that capture behavior in real-world settings, again not fitting the definition of official statistics, as they do not involve standardized data collection by official agencies. Thus, registration of births stands out as the method that is specifically designed for the systematic collection of data that is considered official statistics.