The correct answer is the following: <em>option b. The 19th Amendment expanded the right to vote to about half the population.</em> Adopted on August 18th, 1920, The 19th Amendment to the Constitution of the United States declared that it was illegal for any state to deny the right of vote to citizens of the United States based on their sex. This allowed women to vote for the first time in the history of the nation. It is the only Amendment that expanded the right to vote to half the population of the country, as women are the only group of citizens that represents half or more of the population of the country. All of the others Amendments mentioned in the question granted voting rights to more people, but not to half of the population.