Comprehensive U.S. Government and Political Theory Practice Test

The 19th Amendment is the correct answer because it explicitly states that the right to vote shall not be denied on the basis of sex. Ratified in 1920, this amendment marked a significant milestone in the women's suffrage movement, granting women the legal right to participate in elections at the federal and state levels. Prior to this amendment, women faced numerous obstacles and legal barriers that prevented them from voting, despite their contributions to society and demands for equality.

The other amendments listed address different issues: the 15th Amendment prohibits denying the right to vote based on race, the 21st Amendment repealed Prohibition, and the 24th Amendment prohibits poll taxes in federal elections. Each of these amendments contributed to expanding civil rights in various contexts, but the 19th Amendment specifically focuses on securing voting rights for women, thus making it the correct choice in this context.