Which of the following statements are so related that if one of them is true, the other must be false and vice versa? Choose the correct answer from the options given below:
1.All pitcher-plants are carnivores.
2.No pitcher-plants are carnivores.
3.Some pitcher-plants are carnivores.
4.Some pitcher-plants are not carnivores.
A1 & 4 only ✓ Correct
B3 & 4 only
C1 & 2 only
D2 & 4 only
Correct answer: (A) 1 & 4 only
Explanation
Statements 1 (All pitcher-plants are carnivores) and 4 (Some pitcher-plants are not carnivores) are so related that one's truth forces the other's falsity and back again.
This mutual exclusion with mutual exhaustiveness is the contradictory relation.
Statement 1 is a universal affirmative (A) and Statement 4 is the particular negative (O).
A and O are contradictories, so exactly one of them is true and the other false in every case.
That is the defining feature the question describes.
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