Which of the following statements are logically equivalent?

1.Some animals are birds

2.Some birds are animals

3.Some animals are not non-birds

4.Some animals are non-birds

5.Some non-birds are not non-animals

A1, 2 & 3 only ✓ Correct

B1, 3 & 4 only

C2 & 3 only

D2, 3, 4 & 5 only

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

Explanation

Statements 1, 2 and 3 all express the same particular affirmative.

'Some animals are birds' is the I proposition (Statement 1).

Converting it gives 'Some birds are animals,' valid for I (Statement 2).

Obverting it gives 'Some animals are not non-birds' (Statement 3).

Each keeps an overlap between animals and birds, so the three are equivalent.

'Some animals are non-birds' asserts a different overlap and is not among them.

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