Answer:
B. It can be largely attributed to the fact that individuals who experience union representation are unhappy with it and decide they do not want it.
Step-by-step explanation:
It isn't a fact that most individuals who experience union representation are unhappy with it and they decide to not want the union. So you couldn't attribute this as a fact about the decline in demands for unions. Studies have found that unionized workers remain more time in their jobs in comparison to non unionized.
Bender, K. A., & Sloane, P. J. (1998). Job Satisfaction, Trade Unions, and Exit-Voice Revisited. ILR Review, 51(2), 222–240.