Apple Entered the Music Player Market with Its IPod in 2001

Apple entered the music player market with its iPod in 2001 and by 2014 it had a 70 percent share of this market. However, global MP3 music player unit sales over the past few years have fallen dramatically and were expected to decline further by 2016, as Apple announced it is discontinuing the iPod Classic while it will continue to sell three iPod product lines. Currently, Apple's iPod SBU appears to be a

A) question mark.
B) star.
C) hedgehog.
D) cash cow.
E) dog.