Which of the following statements are so related that they cannot both be false, although they can both be true?

1.Some professors are spiritualists.

2.All professors are spiritualists.

3.No professors are spiritualists.

4.Some professors are not spiritualists.

A2 & 3 only

B2 & 4 only

C1 & 4 only ✓ Correct

D1 & 3 only

Correct answer: (C) 1 & 4 only

Explanation

Statements 1 and 4 cannot both be false though they can both be true, being subcontraries.

Statement 1, some professors are spiritualists, is the I form.

Statement 4, some professors are not spiritualists, is the O form.

I and O stand as subcontraries on the square of opposition.

Subcontraries can be true together but are never false together.

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