Two file servers have run out of local disk space. The internal drives are at capacity and the company has traditionally only used local disks for storage. Which of the following is the MOST cost effective solution to add storage to both servers?（）

• A、Install fiber cards into the servers and add direct attached storage.
• B、Install fiber cards into the servers and implement a SAN solution.
• C、Attach a USB drive to one of the servers.
• D、Add a NAS to the environment