Which of the following statements are logically equivalent?

1.Some animals are birds

2.Some animals are not non-birds

3.Some non-birds are not non-animals

4.Some birds are animals

A2 & 3 only

B2, 3 & 4 only

C1, 2 & 4 only ✓ Correct

D1, 2 & 3 only

Correct answer: (C) 1, 2 & 4 only

Explanation

Statements 1, 2 and 4 all state the same particular affirmative content.

Statement 1 is Some animals are birds, an I proposition.

Statement 2 is its obverse, Some animals are not non-birds, logically equal.

Statement 4 is its converse, Some birds are animals, valid for I.

Statement 3 shifts to non-birds and non-animals invalidly and is not equivalent.

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