What differentiates a user-defined custom dimension from the Entity and Account dimensions?

What differentiates a user-defined custom dimension from the Entity and Account dimensions?

A.
You can only add custom attributes to user-defined custom dimensions.

B.
You assign valid plan types for the user-defined custom dimension at the dimension level.

C.
You assign data types for the user-defined custom dimension at the dimension level.

D.
You cannot: assign security for user-defined custom dimensions.

E.
You can easily delete a user-defined custom dimension in Planning but you cannot delete an
Entity dimension.

Explanation:
User-defined custom dimensions differ from the Entity and Account dimensions in
that you
assign valid plan types at the dimension level, not at the member level. All members of a user
defined custom dimension are valid for plan types assigned at the dimension level.