Final answer:
The subject of this question is Social Studies because it involves a historical letter written by Thomas Jefferson regarding the Missouri Crisis.
Step-by-step explanation:
The letter written by Thomas Jefferson to John Holmes on the Missouri Crisis reflects his profound concern regarding the divisive issue of slavery in the new territories and the potential threat it posed to the union of the United States. Jefferson considered the Missouri question, which involved whether slavery should be allowed in the newly admitted state, a fire bell in the night that awakened him to the risk of disunion. He expressed his fear that the division on the issue would mark the start of a deeper and more permanent schism within the nation, potentially leading to its dissolution. Moreover, he lamented that the efforts and sacrifices of the generation of 1776, which fought for self-government and happiness, might be undone by their descendants through rash and injudicious actions driven by passion rather than reason.