Which of the following statements are logically equivalent?

1.No tigers are non-mammals

2.No mammals are tigers

3.All non-mammals are non-tigers

4.All tigers are mammals

A1, 3 & 4 only ✓ Correct

B1 & 2 only

C1, 2 & 3 only

D2 & 3 only

Correct answer: (A) 1, 3 & 4 only

Explanation

Statements 1, 3 and 4 are logically equivalent.

Start from 4, the A proposition "All tigers are mammals".

Its obversion gives 1, "No tigers are non-mammals".

Its contraposition gives 3, "All non-mammals are non-tigers".

Statement 2 "No mammals are tigers" denies any overlap and contradicts the base.

Obversion and contraposition keep meaning, tying 1, 3 and 4 together.

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