When the U. S. Constitution says "federal law is the supreme law of the land" what does that mean?

The Supremacy Clause is a clause within Article VI of the U.S. Constitution which dictates that federal law is the "supreme law of the land." This means that judges in every state must follow the Constitution, laws, and treaties of the federal government in matters which are directly or indirectly within the

Explanation:

can someone me with this question:  

1) the end of the conflict between the north and the south didn’t just mark the end of a war; it marked the end of an entire way of life.” which statement best describes what this statement means?  

a) the southerners were no longer free and were controlled by the northern states.

b) the industrial economy in the north was not sustainable.

c) slavery became illegal, which changed completely the south’s labor force and the agricultural economy was destroyed.

d) the states decided to relinquish their independence and return to britain’s rule.    

education was essential to the former slaves during reconstruction simply because it enabled their integration into the mainstream community.