In the first half of the 20th century, literacy tests, poll taxes, and grandfather clauses were passed by the southern states in order to

They were passed by the southern states in order to keep most African Americans from voting and violated the equal voting right that was guaranteed by the Fifteenth Amendment.

C)deny suffrage to African Americans.

Even after the Fifteenth Amendment guaranteed voting rights to all Americans regardless of their race, most southern states created obstacles to deny suffrage to African Americans, a process also known as "disenfranchisement" or "disfranchisement." Examples of such obstacles were literacy tests, poll taxes, and the grandfather clause, which all put up barriers meant to prevent black people from exercising their legal rights.

a case involving the laws of a single state.