An administrator is adding additional memory into a server that registers 1GB of memory in the OS and notices that the system has 2GB of memory physically installed； however， the server only shows 1GB of memory during POST.  Which of the following is the MOST likely reason for this？（）

• A、 The OS does not support more than 1GB of memory.
• B、 The system memory has different manufacture dates.
• C、 Two of the memory sticks are defective.
• D、 The server is using memory interleaving.