What type of study design involves observing a population at a single point in time?

Correct Answer: C

Rationale: Cross-sectional studies (C) snapshot prevalence at one time (e.g., surveys). A is retrospective, B is longitudinal, D is experimental.

Correct Answer: C

Rationale: Cross-sectional studies (C) collect data at one time (e.g., survey). A is cohort, B is case-control, D is longitudinal.

Correct Answer: C

Rationale: Cross-sectional studies (C) snapshot data at one time (e.g., surveys). A is retrospective, B is longitudinal, D is experimental.

Correct Answer: C

Rationale: Matching (C) controls confounding in design (e.g., age-matching in case-control). A and B are analysis methods, D reduces observer bias.

Correct Answer: C

Rationale: Beneficence (C) maximizes benefits and minimizes harm (e.g., risk-benefit balance). A is autonomy, B is non-maleficence, D is justice.