The correct answer is 1846. To determine the year in which the Mexican-American War began, you can search for the specific war and its timeline. One way to do this is by using an internet search engine and typing in "Mexican-American War timeline." This will give you multiple sources that provide information about the war, including the start date. In this case, searching for the Mexican-American War timeline will quickly reveal that the war began in 1846. Therefore, the correct answer is 1846.
