What was special about the 1824 election

In the United States presidential election of 1824, John Quincy Adams was elected President on February 9, 1825, after the election was decided by the House of Representatives. The previous few years had seen a one-party government in the United States, as the Federalist Party had dissolved, leaving only the Democratic-Republican Party. In this election, the Democratic-Republican Party splintered as four separate candidates sought the presidency. Such splintering had not yet led to formal party organization, but later the faction led by Andrew Jackson would evolve into the Democratic Party, while the factions led by John Quincy Adams and Henry Clay would become the National Republican Party and later the Whig Party.

the enslaved people onboard suffered from illness with some frequency

d is the best answer for this question.