Final answer:
The former president's statement expresses skepticism and suggests that the Missouri Compromise line was only a temporary solution.
Step-by-step explanation:
The former president's statement to Sara can be characterized as skeptical or doubtful. When he says that the Missouri Compromise line "is a reprieve only, not a final sentence," he likely means that it is a temporary solution or delay, rather than a permanent or definitive resolution. The Missouri Compromise line was established in 1820 to address the issue of slavery in the United States, but it did not ultimately resolve the conflict.