The Jim Crow stereotype harmed African Americans by altering: a. Laws protecting their voting rights b. The public's perception of them c. Laws related to public schools d. Their eligibility to serve in the military

The right choice is:

a. Laws protecting their voting rights.

Explanation:

The Jim Crow laws passed by the state legislatures of several southern states impeded African Americans the full exercise of their political and constitutional rights.  They created poll taxes or literacy tests that made impossible for them to vote in elections, created segregated facilities and denied quality education for blacks. It was a series of  legal dirty tricks to circumvent the 14th Amendment and other federal laws passed after the Civil War.

i would go with the last one