During a planning session， the customer indicates that they intend to build two independent two- Node clusters （cluster ’A’ and ’B’） that will be provided shared storage form an IBM TotalStorage FAStT900 server. The customer intends to present 2 LUNs to cluster ’A’， and 2 LUNs to cluster ’B’. All hosts will be dual attached via fibre.  What additional hardware or software is necessary to make this a valid configuration？（）  

• A、 SAN switches
• B、 Fibre channel Hub（s）
• C、 IBM Storage Manager Agents
• D、 IBM Subsystem Device Driver