Which of the following is a measure of the severity of a disease?

Correct Answer: B

Rationale: Case fatality rate (B) measures severity as deaths among cases (e.g., Ebola). A is new cases, C is total cases, D is deaths broadly.

Correct Answer: B

Rationale: Outbreak investigation (B) identifies sources (e.g., Snow’s pump) for control. A, C, and D are secondary or unrelated.

Correct Answer: C

Rationale: Observational studies (C) observe natural events without intervention (e.g., smoking studies). A, B, and D are experimental.

Correct Answer: C

Rationale: Cohort studies (C) follow disease progression over time (e.g., HIV stages). A is snapshot, B is retrospective, D is interventional.

Correct Answer: C

Rationale: Cross-sectional studies (C) measure prevalence (e.g., diabetes rates). A and B focus on associations, D on interventions.