The core concept tested here is the understanding of the main idea of a complex sentence. The correct answer directly reflects the main idea that the assisted-suicide debate is fueled by the despair of patients whose physical suffering has been prolonged by modern medicine. Option A is incorrect because it contradicts the sentence's implication that modern medicine has prolonged physical agony, not reduced it. Option C is incorrect as it misrepresents the medical community's stance, which is not described as unanimous support for assisted suicide. Option D is incorrect because it presents assisted suicide as the only solution, which is not stated or implied in the sentence.