If 'All college professors are entertaining lecturers' is true in a square of opposition, which of the following can be correctly inferred?

1.'No college professors are entertaining lecturers' is false

2.'Some college professors are not entertaining lecturers' is true

3.'Some college professors are entertaining lecturers' is true

4.'Some college professors are entertaining lecturers' is false

A1 & 2 only

B2 & 3 only

C3 & 4 only

D1 & 3 only ✓ Correct

Correct answer: (D) 1 & 3 only

Explanation

With the A All college professors are entertaining lecturers true, the E is false and the I is true.

A and E are contraries, so a true A makes the E No college professors false, Statement 1.

A and I are related by subalternation, so a true A makes the I Some are true, Statement 3.

The O is the contradictory of A, hence false, so Statement 2 claiming the O true fails.

Only Statements 1 and 3 follow correctly.

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