Why Was It Difficult for Blacks to Find Jobs in the North

Why was it difficult for blacks to find jobs in the North after 1820?

A) There were very few jobs in the North after 1820 due to an economic depression.
B) White immigration increased and employers preferred to hire whites.
C) Racism began in the North only after 1820.
D) Industry, especially the textiles industry, began to shift to the south.