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GATE 2016 CE (CE2) – Question 8

General Aptitude · Analytical Aptitude: Logical Reasoning and Deduction · 2 marks · Multiple choice

Fact 1: Humans are mammals. Fact 2: Some humans are engineers. Fact 3: Engineers build houses. If the above statements are facts, which of the following can be logically inferred? I. All mammals build houses. II. Engineers are mammals. III. Some humans are not engineers.

  1. II only.
  2. III only.
  3. I, II and III.
  4. I only.

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Show answer and explanation

Correct answer: (B) III only.

Explanation

The official key selects **III only, B**. This uses an informal reading of some humans are engineers as some but not all, yielding some humans are not engineers. Under strict predicate logic, some asserts existence without excluding all, so III does not necessarily follow; I and II also do not follow from the given subset relation. Preserve B for grading while recognising this assumption.