Which pattern would be least effective in explaining a complex topic that has no clear resolution?

A problem-solution structure is designed to identify a specific problem and propose one or more solutions, making it most effective when there is a clear resolution to the issue at hand. When dealing with a complex topic that lacks definitive answers or resolutions, this approach may become limiting, as it implies a two-part structure focused on finding solutions, which may not be possible in situations where the complexity of the topic does not allow for straightforward answers.

In contrast, a chronological approach outlines events in the order they occur, which can help clarify processes or developments over time but might not address ambiguity well. The topical pattern breaks down the subject into distinct subtopics, providing comprehensive coverage of various facets, while the cause-effect pattern explores relationships between events or concepts, which can help to elucidate the complexity of a situation. Each of these other methods retains a degree of flexibility to accommodate the nuances of complex subjects that don't have clear resolutions.