CompTIA Server+

Answer - B - A minimum of three drives are necessary to operate a RAID 5 array.

Key Takeaway: RAID 5 combines three or more disks in a way that protects data against the loss of a disk. It is similar to RAID 3, but the parity is not stored on one dedicated drive. Instead, parity information is interspersed across the drive array. The maximum number of drives that can fail in any RAID 5 configuration without losing data is only one. Losing two drives in a RAID 5 array is called a “double fault” and results in data loss.