Which of the following statements are logically equivalent?

1.Some cats are aggressive animals

2.Some aggressive animals are cats

3.Some cats are not non-aggressive animals

4.All cats are aggressive animals

A3 & 4 only

B1, 2 & 4 only

C2 & 4 only

D1, 2 & 3 only ✓ Correct

Correct answer: (D) 1, 2 & 3 only

Explanation

Statements 1, 2 and 3 all express the same particular affirmative about cats and aggressive animals.

Statement 1 is Some cats are aggressive animals, the particular affirmative I.

Statement 2 is its converse, Some aggressive animals are cats, valid for an I proposition.

Statement 3 is its obverse, Some cats are not non-aggressive animals, meaning preserved.

Statement 4 is the stronger universal All cats are aggressive animals, not equivalent, so it is excluded.

Conversion and obversion keep the truth of an I proposition intact.

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