Which of the following statements are logically equivalent? Choose the correct answer from the options given below.

1.No metals are gases

2.No gases are metals

3.No metals are non-gases

4.All metals are non-gases

A1, 2 and 4 only ✓ Correct

B1, 2 and 3 only

C2, 3 and 4 only

D1 and 2 only

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

Explanation

Statements 1, 2 and 4 all express the very same proposition.

'No metals are gases' and 'No gases are metals' are converses, and conversion of E is valid.

'All metals are non-gases' is the obverse of 'no metals are gases'.

Both obversion and conversion of the E form preserve the original meaning.

Statement 3, 'no metals are non-gases', instead asserts that all metals are gases, a different claim.

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