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

Statement 1 and Statement 4 are sub-contraries and form the required pair.

The relation sought bars both from being false but permits both being true.

Statement 1 is the particular affirmative, Statement 4 the particular negative.

On the square of opposition the two particular propositions are sub-contraries.

At least one of them must be true, so they cannot both be false together.

This is precisely the sub-contrary relation the question specifies.