Which statement is true about the component-cause model?

• A. A necessary cause must be present in every case.
• B. A sufficient cause is a single factor that always causes disease.
• C. A component-cause is one factor that, in combination with others, contributes to a sufficient cause.
• D. A disease occurs only when all possible factors are present.

Answer: (C)

In the component-cause (causal-pie) view of disease, a disease emerges when one complete set of factors—one sufficient cause—is present. Each factor inside that set is a component-cause: it contributes to the disease, but on its own may not cause disease. The statement that a component-cause is one factor that, in combination with others, contributes to a sufficient cause is exactly what this model describes. It emphasizes that diseases arise from specific combinations of factors, not from any single factor alone, and not from all possible factors at once.

Why the other ideas don’t fit: a necessary cause would have to be present in every possible complete set, which isn’t always the case because there can be multiple distinct sufficient sets sharing no common single factor. A sufficient cause can be a complete set of factors, not just a single factor, and even when it is a single factor, that factor would only cause disease whenever that complete set is present—so the blanket phrasing that a single factor "always" causes disease is too narrow. And disease doesn’t require all possible factors to be present—only the complete set that constitutes one sufficient cause.