Which of the following statements are equivalent?

1.All plants are living organisms

2.No plants are non-living organisms

3.Some plants are living organisms

4.All non-living organisms are non-plants

A1, 2 & 4 only ✓ Correct

B1 & 3 only

C2, 3 & 4 only

D3 & 4 only

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

Explanation

The A All plants are living, its obverse, and its contrapositive all carry the same meaning.

Obverting the A gives No plants are non-living organisms, Statement 2.

Taking the contrapositive of the A gives All non-living organisms are non-plants, Statement 4.

Both obversion and contraposition of an A proposition are valid and truth-preserving.

The I in Statement 3 is only a subaltern, weaker than the A, so it is not equivalent.

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