Exam 1z0-083 topic 1 question 94 discussion

Actual exam question from Oracle's 1z0-083

Question #: 94
Topic #: 1

Which two are true about poorly performing SQL statements and their tuning in Oracle database instances? (Choose two.)

A. SQL statements performing many physical I/Os can always have their performance improved by creating indexes.
B. SQL statements doing only logical reads never require tuning because they do no physical I/O.
C. The solution that best optimizes one SQL statement can degrade the performance of others.
D. SQL statements doing joins always do more physical I/O than single table queries.
E. Poorly performing SQL statements can be tuned automatically by the Oracle server.