How did enslavers and pro-slavery business people stir up pro-slavery sentiment in northern cities?

select the best answer from the choices provided.
a.
they urged congress to pass the fugitive slave act of 1850, which would employ many people in the north.
b.
they threatened white workers with the prospect of free african americans taking their jobs.
c.
they supported sending free african americans to africa, which would open up jobs.
d.
all answers are correct.