Explanation:
The main goal in the buffer cache tuning is minimize physical reads.
Incorrect Answers:

2: The buffer cache hit radio is definitely affected by data or application design.
3: The buffer cache hit ratio will degrade with the use of full table scans.
4: There is some amount of db block buffers in the SGA after reaching it the buffer cache will be degrade, not improve. That's why we use V$RECENT_BUCKET view statistics to find optimal number of db block buffers in the SGA.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 859-873. Chapter 18: Tuning Memory and Operating System Use

---