You want to track and store all transactional changes to a table over its lifetime. To accomplish this task， you enabled Flashback Data Archive with the retention of 5 years. After some time， the business requirement changed and you were asked to change the retention from 5 years to 3 years. To accomplish this， you issued the following command：   ALTER FLASHBACK ARCHIVE fla1 MODIFY RETENTION 3 YEAR；   What is the implication of this command？（）

• A、 The command produces an error because the retention time cannot be reduced.
• B、 All historical data is retained but the subsequent flashback data archives are maintained for only three years.
• C、 All historical data is purged and the new flashback data archives are maintained for three years.
• D、 All historical data older than three years is purged from the flashback archive FLA1.