Understanding Necessary and Sufficient Causes in Disease Development

Factor A, B, or C can each individually cause a certain disease without the other two factors but only when followed by exposure to factor X. Exposure to factor X alone is not followed by the disease, but the disease never occurs in the absence of exposure to factor X.Factor X is:a. A necessary and sufficient causeb. A necessary but not sufficient causec. A sufficient but not necessary caused. Neither necessary nor sufficiente. None of the above

B – A necessary but not sufficient cause

The correct answer to this question is option B: A necessary but not sufficient cause.

Explanation:
In this scenario, factors A, B, or C can cause the disease individually without the other two factors. This means that each of them is sufficient to cause the disease. However, the disease only occurs when followed by exposure to factor X. This means that factor X is necessary for the disease to occur but alone is not enough to cause it. Therefore, factor X is a necessary but not sufficient cause of the disease.

Option A, “A necessary and sufficient cause,” is incorrect because although factor X is necessary, it is not sufficient to cause the disease on its own.

Option C, “A sufficient but not necessary cause,” is incorrect because factors A, B, or C are sufficient causes of the disease individually without factor X.

Option D, “Neither necessary nor sufficient,” is incorrect because factor X is necessary for the disease to occur but not sufficient on its own, as discussed above.

Option E, “None of the above,” is incorrect because option B is the correct answer.

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