In a recent study, researchers sent $5,000$ fictitious resumes to companies advertising in Chicago and Boston. Applicants with "black$-$sounding" names were $50\%$ less likely to be called for an interview than those with "white$-$sounding" names. This unfair treatment based on the group to which someone belongs $($or seems to belong$)$ is called

A$.$ prejudice.

B$.$ egoism.

C$.$ inoculation.

D$.$ discrimination.