Why did black Americans migrate to northern cities during World War I?

Why did black Americans migrate to northern cities during World War I?
 
  A)  The federal government had used the wartime emergency as an opportunity to end southern sharecropping.
  B)  Southern blacks knew that race relations in the North were idyllic compared with those in the South.
  C)  They were seeking the economic opportunities afforded by northern industrial expansion.
  D)  They had been told that northern agriculture was more prosperous than southern agriculture.
  E)  They knew of the northern race riots and decided to move north to help their brothers.