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

1.All physicists are outstanding teachers

2.No physicists are outstanding teachers

3.Some physicists are outstanding teachers

4.Some physicists are not outstanding teachers

A1 & 2 only ✓ Correct

B2 & 4 only

C1 & 3 only

D3 & 4 only

Correct answer: (A) 1 & 2 only

Explanation

Statements 1 and 2 are contrary to each other.

Statement 1 "All physicists are outstanding teachers" is an A proposition.

Statement 2 "No physicists are outstanding teachers" is an E proposition.

A and E are contraries on the square of opposition.

They cannot both be true, yet both may be false together.

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