Why Were Some Slaves Allowed to Work in Towns or Cities

Why were some slaves allowed to work in towns or cities?

A) Slaveowners needed the extra income.
B) Slaveowners usually did not have enough work for them to do on the plantation.
C) Southern reformers wanted slaves to learn new skills for later in life.
D) Slaveowners believed that it would be a way for slaves to "let off some steam" and would therefore prevent slave uprisings.
E) They were in steady demand to work in ports, on the rivers, and in mining and lumbering.