Which of the following propositions are so related that they cannot both be true although they may both be false ?

1.All cars are vehicles.

2.Some cars are vehicles.

3.No cars are vehicles.

4.Some cars are not vehicles.

A1 & 4 only

B1 & 3 only ✓ Correct

C3 & 4 only

D2 & 3 only

Correct answer: (B) 1 & 3 only

Explanation

Statements 1 (All cars are vehicles) and 3 (No cars are vehicles) cannot both be true though both can be false.

Statement 1 is the universal affirmative (A) and Statement 3 the universal negative (E).

A and E are contraries on the square of opposition.

Contraries block joint truth, since all and none cannot both hold, yet allow joint falsity when only some are.

This not both true yet possibly both false pattern marks the contrary relation.

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