Which of the following best exemplifies a focused research question?

The choice that exemplifies a focused research question is indeed the one concerning how cognitive-behavioral therapy affects anxiety levels in adolescents. This question is specific and clearly delineates the population of interest (adolescents), the intervention being studied (cognitive-behavioral therapy), and the outcome being measured (anxiety levels).

A focused research question typically narrows down a broad topic into specific variables and a clear context, allowing for targeted research and analysis. It facilitates the formulation of precise hypotheses and the design of an appropriate study. The aspect of cognitive-behavioral therapy suggests a particular methodology and theoretical framework, while the mention of anxiety levels indicates a measurable outcome.

In contrast, the other options present broader and more generalized inquiries. For example, asking about the impacts of education on society encompasses a vast range of variables and outcomes, thus lacking focus. Similarly, inquiring about the types of therapies that exist for mental health does not direct attention to a specific therapy or its effects, making it too broad for concentrated research. Lastly, the question about why people experience mental health issues addresses a complex and multifaceted subject without honing in on particular factors or populations, which is also indicative of a less focused research question.