GATE 2021 CH – Question 9
Given below are two statements 1 and 2, and two conclusions I and II.
Statement 1: All bacteria are microorganisms.
Statement 2: All pathogens are microorganisms.
Conclusion I: Some pathogens are bacteria.
Conclusion II: All pathogens are not bacteria.
Based on the above statements and conclusions, which one of the following options is logically CORRECT?
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Correct answer: (D) Neither conclusion I nor II is correct.
Explanation
Let B, P and M denote bacteria, pathogens and microorganisms. The premises give only **B is contained in M** and **P is contained in M**. They do not specify the overlap between B and P.
If B and P are disjoint, conclusion I fails; if they overlap, the reading of II as “no pathogens are bacteria” fails. Thus neither conclusion follows individually from the premises, which supports **D**.
There is a wording ambiguity: if C asks whether “some P are B” or its negation must hold, that disjunction is exhaustive. The phrase “All pathogens are not bacteria” is itself ambiguous between “none” and “not all”. This item requires review.