单项选择题 Multiple expansion cards are installed in a rack mount 1U server. All expansion cards stop working simultaneously.  Which of the following is the MOST likely cause of the problem？（）

单项选择题 Which of the following offers the MOST redundancy for a system but is also very costly?（）

单项选择题 A system administrator needs to maintain 1.2TB of storage for a database server. There are six 250GB drives available in the server for storage space. Which of the following RAID configurations would be the BEST choice given that performance and fault tolerance are important factors?（）