People may unconsciously harbor negative racial associations. this best illustrates the subtle nature of prejudice

I believe the correct answer is implicit prejudice.

People may unconsciously harbor negative feelings and/or beliefs about a group on basis of the race, sex, age or ethnicity. This unawareness of negative beliefs or feelings best illustrates the subtle nature of the implicit prejudice (or more commonly: the prejudice).

answer; the civil right act of 1964;