Which amendment finally made it unconstitutional to deny suffrage based on sex?

A. Fourteenth Amendment

B. Fifteenth Amendment

C. Nineteenth Amendment

D. Twenty-First Amendment

The correct answer is: the Nineteenth Amendment.

Women gained voting rights in the US later than people of colour, as this Amendment was passed in 1920 and the Fifteenth Amendment, which prohibits racial discrimination when voting, was passed in 1870.