Using the table — Sick patients: 870 test-positive (true positive), 10 test-negative (false negative); Healthy patients: 45 test-positive (false positive), 2100 test-negative (true negative) — the SENSITIVITY is approximately:

Correct answer: A. 99%

• A. Correct. Sensitivity = TP / (TP + FN) = 870 / (870 + 10) = 870/880 = 0.989 ≈ 99%.
• B. 80% does not match the calculation.
• C. 90% understates the true value (≈98.9%).
• D. 95% is incorrect; the calculated sensitivity is ≈99%.

Note: The source key marked 95%, but 870/880 = 98.9% ≈ 99%. The correct answer is 99% (the source contained a calculation error).