A company wants a mixed tier pool to optimize the use of their Flash, 10k RPM and 15k RPM drives. They want
the Flash drives configured in RAID 5, the 10k RPM drives in RAID 6, and the 15k RPM drives in RAID 5.
Why can only two tiers in the pool be created?

A.
The 10k and 15k drives are the same tier

B.
Flash drives cannot be used in a pool

C.
A pool is either RAID 5 or RAID 6

D.
FAST Cache is also configured