_____ research combines qualitative and quantitative research and should be accompanied by a clear rationale.

Mixed-methods research is a methodology that integrates both qualitative and quantitative research approaches within a single study. This type of research is particularly valuable because it allows for a comprehensive understanding of a research problem by leveraging the strengths of both data types. Qualitative research provides in-depth insights into participant experiences and perspectives, while quantitative research offers measurable data that can be statistically analyzed.

A clear rationale is crucial when conducting mixed-methods research. This ensures that the researcher clearly articulates the reasons for choosing to utilize both qualitative and quantitative methods, how they will be integrated, and what insights are expected to be gained from this combination. This approach can help to confirm findings from one method using the other and enables a more robust analysis by providing a fuller picture of the research question or problem.

In contrast, other options like multilevel, multimodal, or service-oriented research do not specifically emphasize the combination of qualitative and quantitative data. They focus on different aspects of research methodologies or frameworks without necessarily implying the integration of both data forms.