Which statement does not describe a method whites used to keep blacks from exercising their rights?

a.
they started a "separate but equal" policy to keep the races apart.

b.
they passed "black codes" after the civil war that made free blacks little more than slaves.

c.
they formed hate groups, such as the ku klux klan, to terrorize blacks.

d.
they gave generous payments to blacks who agreed to move to africa or canada.