De Morgan's Law states that (A∪B)c(A \cup B)^c(A∪B)c is equal to:
Ac∩BcA^c \cap B^cAc∩Bc
Ac∪BcA^c \cup B^cAc∪Bc
A∩BA \cap BA∩B
(A∩B)c(A \cap B)^c(A∩B)c