Which of the Following Can at Least Partially Explain the Decline

Multiple Choice

Which of the following can at least partially explain the decline in union density rates in the United States since the 1960's?

A) Employment in traditionally unionized industries such as manufacturing has decreased.
B) Employment in service and knowledge industries has declined.
C) Employment growth in the north has been faster than employment growth in the south.
D) Educated workers are more likely to unionize than uneducated workers.