Which analytical problem might be addressed in such reports?

The choice of identifying "Why does X happen?" as the analytical problem addressed in reports is correct because it delves into causation and underlying factors that lead to a particular event or phenomenon. Analytical reports are often designed to explore reasons behind trends, behaviors, or results, aiming to provide insights into complex situations. By understanding causality, decision-makers can implement strategies to modify the situation, address issues, or replicate successes.

In contrast, the other options focus on definitions, attributions, or locations, which are more descriptive rather than analytical. "What is X?" seeks to define a concept, "Who is responsible for X?" identifies accountability, and "Where is X located?" specifies physical or situational attributes. While these questions are relevant in gathering information, they do not engage with the analytical depth required to explore "why," which is essential for problem-solving and strategic planning within reports.