You are maintaining the PROD database of TeleSoft Corporation. You have initialized the following DB_BLOCK_CHECKING parameter in the init.ora file：  DB_BLOCK_CHECKING = TRUE；  What will be the result of setting this parameter？（）

• A、 Only data blocks of the SYSTEM tablespace will be checked.
• B、 Only data blocks of the SYSAUX tablespace will be checked.
• C、 A checksum will occur only on the checkpoint.
• D、 A checksum will occur every time a block is modified.