Two database users, Jack and Bill, are accessing the SupportCenter STAFF table of the SupportCenter DB database. When Jack modifies a value in the table, the new value is invisible to Bill. Which is the modified value invisible to Bill?（）

• A、The modified data are not available on disk.
• B、The modified data have been flushed out from memory.
• C、The modified rows of the SupportCenter STAFF table have been locked.
• D、Jack has not committed the changes after modifying the value.
• E、Both users are accessing the database from two different machines.