Explanation:
The frequency of checkpoints will be decreased if the value of the FAST_START_IO_TARGET will be increased: Oracle will need more time to recover database after instance crash.
Incorrect Answers:

1: The number of redo log groups has no relation with frequency of checkpoints.
2: DB_BLOCK_SIZE buffer has nothing to do with checkpoints.
4: By decreasing the value of the REDO_LOG_BUFFERS you will INCREASE frequency of checkpoints because redo log files will be filled with updates more quickly.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 902. Chapter 19: Tuning Database Utilization

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