In the Context of Voting, the Practical Effect of the Grandfather

In the context of voting, the practical effect of the grandfather clause was to​

A) ​permit African Americans to vote, as long as their family members had voted in a presidential election.
B) ​deny voting rights to African Americans, while maintaining the right of poor white citizens to vote.
C) ​provide a procedure for African Americans to follow, as long as they arrived early at the polling place.
D) ​deliver information to African Americans regarding upcoming votes, while maintaining a separate location for voting.