Contraries are propositions such that:

A) they could not both be false, but could both be true
B) they could not both be true, but could both be false
C) if the universal is true, then the particular must be true
D) if the universal is false, then the particular must be false
E) they cannot both be true and they cannot both be false

Contraries are propositions that cannot both be true but could both be false. For example, "All cats have fur" and "No cats have fur" are contraries, as they cannot both be true but there could be some cats with fur and some without. Option A describes subcontraries, option C describes the relationship between universal and particular affirmatives, option D describes the relationship between universal and particular negatives, and option E describes the relationship between contradictories.