Which Exadata feature uses Flash as a parallel write cache to Disk Controller Cache?

Which Exadata feature uses Flash as a parallel write cache to Disk Controller Cache?

A.
Exadata DRAM

B.
InfiniBand network cache

C.
high performance SAS disks

D.
Smart Flash Log

E.
Hybrid Columnar Compression

Explanation:
http://www.oracle.com/technetwork/database/availability/databaseawareflash-2030367.pdf(slide 21)