Which RAID level provides the most redundancy?

Which RAID level provides the most redundancy?

A.
RAID4

B.
RAID5

C.
RAID1

D.
RAID0

Explanation:

See http://en.wikipedia.org/wiki/RAID
a,b) only 1 disk may fail, regardless how many disks are in the RAID
d) no disk may fail
c) n – 1 disks may fail