Going totally wrong direction:
I think electronic disks are faster than magnetic disk so ans should be d
answered Jul 29, 2016 by qwertyui
The electronic r definitely faster coz they r ram or flash (https://en.wikipedia.org/wiki/Solid-state_drive ) magnetic are 2dary & D option is for only competition with A so we compare optical & magnetic CDs & HDD.
Magnetic disk storage has been optimized for high speeds. DVDs and CDs access data fast enough to play movies and music, but are much slower than a magnetic disk.
So, Ye answer is D) if ur only concern was Key.
& @vijaycs Veteran neither hard disk nor CD(optical sir) is electronic.