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 A 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
D – Neither necessary nor sufficient
The correct answer is (b) a necessary but not sufficient cause.
Explanation:
According to the given scenario, the disease only occurs when one of the three factors (A, B, or C) is present followed by exposure to factor X. This indicates that any of these three factors alone are necessary but not sufficient to cause the disease.
Since the disease never occurs in the absence of exposure to factor X, it can be concluded that factor X is also necessary but not sufficient to cause the disease.
Therefore, factor A (or B or C) can be considered a necessary but not sufficient cause of the disease, whereas factor X can be considered necessary for the occurrence of the disease.
Option (a) is incorrect because if factor A were a necessary and sufficient cause, then the disease would occur regardless of the presence or absence of factor X.
Option (c) is incorrect because if factor A were sufficient but not necessary, then the disease would occur even in the absence of factor X.
Option (d) is incorrect because factor A is necessary for the disease to occur, although it is not sufficient.
Option (e) is incorrect as the correct answer is (b).
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