Which of the following is an example of selection bias?

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: D

Rationale: Vulnerable populations need all (D): consent (A), rights protection (B), and safeguards (C) (e.g., children).

Correct Answer: B

Rationale: Diagnostic tests (B) confirm or rule out disease (e.g., biopsy for cancer). A, C, and D are unrelated.

Correct Answer: C

Rationale: Tertiary prevention (C) includes rehab post-disease (e.g., stroke therapy). A is primary, B is secondary.

Correct Answer: B

Rationale: Risk factor (B) increases disease likelihood (e.g., smoking). A is protective, C is treatment, D is measure.