In Venn diagrams, an X is used to indicate that:

A) something doesn't exist
B) something exists
C) you've made an error in that part of the diagram
D) the proposition does not have a subject
E) the proposition does not have a predicate

Venn Diagrams

Diagrams consisting of overlapping circles, used to visually represent relationships between different sets or groups.

Existence

The state or fact of being real or living or of being present.

X

Often used to represent an unknown variable or quantity in mathematical equations and other analytical contexts.