Which Statement Best Explains Why Unions Have Declined Rapidly in the U.S

Which statement best explains why unions have declined rapidly in the U.S. but have maintained strength in Canada?

A) The American economy has shifted away from manufacturing, but the Canadian economy has not.
B) More Canadian families benefit from a stay-at-home parent who does not work.
C) Canadian political parties have little power to change legislation.
D) Canada has over a dozen labour laws, while the U.S. has only one.