What type of study design involves randomly assigning participants to different interventions?

Correct Answer: D

Rationale: Randomized controlled trials (D) assign interventions randomly to test effects (e.g., drug trials). A, B, and C are observational.

Correct Answer: B

Rationale: Cross-sectional studies (B) measure prevalence at one time (e.g., obesity rates). A requires time, C and D need longitudinal data.

Correct Answer: B

Rationale: Descriptive studies (B) collect quantitative data (e.g., case counts) to describe patterns. A is qualitative, C is experimental, D is broad.

Correct Answer: B

Rationale: Observational studies (B) watch natural events (e.g., smoking-disease links). A and D are experimental, C is a byproduct.

Correct Answer: A

Rationale: Descriptive studies often collect qualitative data (A) to describe patterns (e.g., case reports), though quantitative (B) is also common. C and D are less typical.