Which two are true about virtual columns?

Regarding the properties and capabilities of virtual columns in Oracle Database:

C. They can be indexed: In Oracle, virtual columns can indeed be indexed. This allows for performance optimization on queries that utilize these columns, despite the fact that their values are derived and not stored physically.

D. They cannot have a data type explicitly specified: The data type of a virtual column is derived from the expression used to define it. Therefore, it is not specified explicitly but is inferred from the expression itself.

Incorrect options:

A: Virtual columns cannot be referenced in the WHERE clause of UPDATE or DELETE statements because they are not stored and cannot be individually modified.

B: Virtual columns cannot be referenced in the SET clause of an UPDATE statement since they are derived from other column values and cannot be updated directly.

E: Virtual columns cannot reference other virtual columns in their expressions due to the potential for recursive and complex dependencies.