The 24th amendment to the constitution made illegal in the united states.
a.
poll taxes
b.
literacy tests
c.
voting fraud
d.
impersonation

A. Poll Taxes. 

The 24th amendment prohibits both prohibits Congress and the states to do that. 

It's A. Poll taxes

Section 1.

The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any state by reason of failure to pay any poll tax or other tax.

Section 2.

The Congress shall have power to enforce this article by appropriate legislation.