Which of the following statements are logically equivalent ?

1.All non-flowers are non-tulips.

2.No tulips are non-flowers

3.All non-tulips are non-flowers

4.All tulips are flowers

A1, 2 & 3 only

B2 & 3 only

C3 & 4 only

D1, 2 & 4 only ✓ Correct

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

Explanation

Statements 1, 2 and 4 are logically equivalent.

Take "All tulips are flowers" as the base universal affirmative.

Its obverse is "No tulips are non-flowers", which is Statement 2.

Its contrapositive is "All non-flowers are non-tulips", which is Statement 1.

Obversion and contraposition both preserve truth, so these three say the same thing.

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