What is the main idea of the passage about Sickle-Cell Anemia?
Correct Answer: D
Rationale: The correct answer is D. The passage focuses on describing sickle-cell anemia as a painful and inherited disease. It details how the abnormal sickle-shaped cells cause symptoms like bone pain, fever, and fatigue. While bone pain is mentioned as a symptom, it is not the main idea of the passage. Choice A is incorrect. Choice B, which mentions oxygen transport, is not the main idea but a general concept. Choice C, stating genetically inherited diseases affect thousands, is too broad and does not focus on the specifics of sickle-cell anemia. Therefore, D is the most precise choice.