Which statement about expression-based indexes is true?

A.
The RUNSTATS command cannot be used to collect statistics for expression-based indexes.

B.
Expression-based indexes must always be defined as UNIQUE to prevent duplicate index keys.

C.
Expression-based index keys consist of a concatenation of one or more specified table
columns.

D.
The index key values of expression-based indexes are not the same as the values in the
corresponding table columns.