According to Evans and Tilley, What Is the Main Reason

According to Evans and Tilley, what is the main reason why vote choice in the UK today is less tied to class identification than before?

A) Labour shifted away from its core voting bloc under Tony Blair.
B) Classes are less homogenous now than they previously-.
C) Many workers in sectors that traditionally voted Labour have lost their job.
D) Labour lost power in 2010 to the Conservatives.