An outbreak of disease that occurs worldwide and affects a large number of people is called a:

Correct Answer: C

Rationale: A pandemic (C) is a global outbreak (e.g., 1918 flu). Endemic (A) is constant presence, epidemic (B) is regional excess, and cluster (D) is a localized group.

Correct Answer: A

Rationale: Incidence rate (A) measures new cases over time. B, C, and D are test performance metrics, not frequency.

Correct Answer: B

Rationale: Cohort studies (B) track groups over time for disease onset (e.g., Framingham). A is case-control, C is cross-sectional, D is RCT.

Correct Answer: C

Rationale: Cohort studies (C) compare exposed vs. unexposed groups for outcomes (e.g., cancer rates). A is snapshot, B is retrospective, D is experimental.

Correct Answer: A

Rationale: Case reports (A) describe individual cases (e.g., new disease). B, C, and D are analytical or experimental.