Examine the following output： SQL> SELECT index_name，status FROM dba_indexes WHERE status=’UNUSABLE’； INDEX_NAME STATUS------------------------------ ----------- EIND UNUSABLE Which two statements about the above index are true（）
- AIt is ignored by the query optimizer.
- BIt is not used while the index is being rebuilt.
- CThe index cannot be rebuilt， and has to be re-created.
- DThe index is automatically rebuilt when used the next time