Among the following, there are two statements which cannot be true together but can be false together. Select the code that represents them.

Statements 1 (All bats are mammals) and 4 (No bats are mammals) cannot be true together yet can be false together.

These are the universal affirmative (A) and universal negative (E) about the same terms.

A and E are contraries on the square of opposition.

Contraries exclude joint truth, since all and none cannot both hold, but allow joint falsity when only some bats are mammals.

That pattern of not both true yet possibly both false is precisely the contrary relation.