The practice that assumes that nonwhite americans are more likely to commit crimes than white americans.

The practice that assumes that nonwhite Americans are more likely to commit crimes than white Americans is racial profiling .

Racial profiling refers to the act of suspecting or targeting a person of a specific race based on observed or assumed features or behavior of a racial or ethnic group, rather than on individual suspicion.  

Racial profiling is a longstanding and deeply troubling national problem in the United States.

while it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton.

explanation:

before eli whitney's invention of the cotton gin, picking and cleaning cotton was a slow, labor-intensive job. workers, usually slaves, had to pick the seeds from the cotton fibers by hand. this invention made it possible to grow large amounts of cotton on big farms and make money.

(d) take jobs from american workers.