The term 'natural history of disease' refers to:

Correct Answer: A

Rationale: Natural history (A) is disease progression without intervention (e.g., HIV stages). B, C, and D are unrelated aspects.

Correct Answer: C

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

Correct Answer: B

Rationale: Controls (B) in case-control studies lack the disease for comparison. A is cases, C and D confuse exposure status.

Correct Answer: B

Rationale: Selection bias occurs when participant selection distorts exposure-outcome relationships, but B (misclassification) is information bias. A (loss to follow-up) is attrition bias, often considered a form of selection bias in cohorts, yet the answer key lists B. C and D are recall and observer biases. The key may be incorrect; A aligns better with selection bias.

Correct Answer: C

Rationale: Matching (C) controls confounding in design (e.g., sex-matching). A is analysis, B is broad, D includes analysis methods.