Fill in the blank. a poll tax and tests were used by the south to keep african americans from voting following the civil war.

The answer is literacy. Poll tax and literacy tests were introduced under the Jim crow laws.

this may help you further understand:

https://quizlet.com/17639815/civil-rights-flash-cards/

"One of the jim crow laws. Those who wanted to vote were asked to read a passage of the bible or the constitution (for example); it was incredibly biased against blacks, forcing them to read more difficult passages.

literacy tests"

And this too use this if needed