The correct answer is:
C. If no candidate receives a majority of the vote in the first round of elections, a runoff is held between the two candidates with the most votes in the first round.
Explanation:
1. In Mexico, the president is not elected through a plurality formula (A) where the candidate with the most votes in a single round wins.
2. The Mexican president is not chosen using a majority formula (B) requiring more than 50 percent of the vote to win outright.
3. Instead, if no candidate receives a majority of the vote in the initial election, a runoff (C) is conducted between the top two candidates with the highest number of votes.
4. The runoff system ensures that the eventual winner secures a majority of the votes, thereby legitimizing their presidency.
5. Option D, which mentions a candidate needing at least 25 percent of the vote in two-thirds of Mexico's states, does not accurately describe the election process for the Mexican president.