All of the Following Have Been Given as Possible Reasons

All of the following have been given as possible reasons for a gradual decline in union membership except that _______

A) firms moving to the Sunbelt tend to hire nonunion workers.
B) federal laws make union membership difficult.
C) heavily unionized industries have not been growing as rapidly as nonunion industries.
D) the largest growth seems to be in nonunion service industries.
E) workers do not share the need to unionize because management satisfies their needs better today.