Which of the following statements are such that they cannot both be false although they can both be true ?

Statements 2 (Some cows are bovines) and 3 (Some cows are not bovines) cannot both be false though they may both be true.

Statement 2 is the particular affirmative (I) and Statement 3 the particular negative (O).

I and O stand as sub-contraries on the square of opposition.

Sub-contraries permit joint truth but forbid joint falsity, since at least one of some are and some are not must hold.

This not both false yet possibly both true pattern is the sub-contrary relation.