The election of african americans to office sharply declined beginning in the late 1870s and 1880s because of
a) literacy tests
b) poll taxes
c) intimidation by whites
d) all answers are correct.

The best answer is D

Violence - Black who tried to vote were threatened , beaten and killed. Their families were also harmed. Sometimes, their homes were burned down. Often, they lost their jobs or were thrown off their farms.

Poll tax -  In southern states , many blacks could not vote because they could not afford the  poll tax which amounted to $ 25  to $50 in today's money.

Literacy tests - Many black and white people could not read or write. White officials usually claimed that whites  who were illiterate could understand what was being read to them  even though they couldn't read and so were still allowed to vote.

But when it came to illiterate blacks, the white officials claimed they could not  even understand what was read to them,  and on the basis of that, they were not allowed to vote.

porter is writing economic history because he is focusing on the cost of developing vaccines.