Final answer:
The U2 album that unexpectedly appeared in iTunes accounts in 2014 is 'Songs of Innocence'.
Step-by-step explanation:
The U2 album that appeared for free in everyone's iTunes account in 2014 is b) Songs of Innocence. The album's surprise release was a significant moment in music distribution history and received mixed reactions from iTunes users, with some appreciating the gift and others seeing it as intrusive. The release coincided with an Apple event wherein the iPhone 6 and Apple Watch were unveiled.
The name of the U2 album that showed up for free in everyone's iTunes account in 2014 was Songs of Innocence.