Regarding the Interrelationship of Federal and State Employment Laws

Multiple Choice

Regarding the interrelationship of federal and state employment laws:

A) state laws must be identical to federal law or the state law is void
B) states may pass laws which reduce employee rights, but may not enact laws that expand employee protections granted in federal laws
C) states may pass laws which expand employee rights, but may not enact laws that reduce employee protections granted in federal laws
D) employment law is exclusively a federal domain, so states may not enact laws when federal law already exists