What type of RAID is RAID 2?

What type of RAID is RAID 2?

• Byte-level striping with dedicated parity.
• A striped set from a series of mirrored drives.
• Block-level striping with dedicated parity.
• Bit-level striping with dedicated Hamming-code parity. 

EXPLANATION

RAID 2
RAID 2 consists of bit-level striping with dedicated Hamming-code parity. All disk spindle rotation is synchronized and data is striped such that each sequential bit is on a different drive. Hamming-code parity is calculated across corresponding bits and stored on at least one parity drive. This level is of historical significance only; although it was used on some early machines (for example, the Thinking Machines CM-2), as of 2014 it is not used by any commercially available system.
RAID 2

SOURCE

https://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_2