What would you recommend to influence the selectivity calculated by the optimizer?

The columns CUST_CITY, CUST_STATE_PROVINCE, and COUNTRY_ID are frequently used
together in the WHERE clause of the queries. The CUSTOMERS table is a big table with 20 GB of
data. You notice that the selectivity for these three columns varies from the selectivity that the
optimizer calculates. What would you recommend to influence the selectivity calculated by the
optimizer?

A.
creating function-based indexes by concatenating all the columns

B.
updating histogram statistics for these columns by using the
DBMS_STATS.GATHER_TABLE_STATS procedure

C.
using the DBMS_STATS.CREATE_EXTENDED_STATSfunction to create a virtual column and
create index on the virtual column

D.
using the DBMS_STATS.CREATE_EXTENDED_STATSfunction to create a virtual column and
the DBMS_STATS.GATHER_TABLE_STATS procedure to collect statistics on the virtual column