Which of the following statements are sub-contraries?

1.All nurses are caring human beings

2.No nurses are caring human beings

3.Some nurses are caring human beings

4.Some nurses are not caring human beings

AI and II only

BI and IV only

CII and III only

DIII and IV only ✓ Correct

Correct answer: (D) III and IV only

Explanation

Statement 3 and Statement 4 are the sub-contraries.

Sub-contraries are the two particular propositions of the square.

Statement 3 is the particular affirmative, Statement 4 the particular negative.

They can both be true together about the same subject.

But they cannot both be false, since at least one must hold.

This pair of particulars is precisely the sub-contrary relation.

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