Why is the query using a full table scan instead of an index scan?

You are working on a decision support system (DSS). The index is available on the COUNTRY_ID
column of the CUSTOMERS table.View the Exhibit and examine the parameter settings and the
query execution plan.

Why is the query using a full table scan instead of an index scan?

A.
because the histogram statistics for the COUNTRY_ID column are not updated

B.
because the index statistics for the index on the COUNTRY_ID column are not current

C.
because the DB_FILE_MULTIBLOCK_READ_COUNT initialization parameter is set to a higher
value

D.
because the optimizer predicts that most of the blocks in the tableare accessed. Therefore, it
uses a full table scan, even though indexes are available.