The correct answer is C). Disintegrate.
The phrase referred in the question is from Abraham Lincoln when he was debating with Stephen A. Douglas. When Lincoln accepted the Republican nomination to run against Stephen A. Douglas, he firmly affirmed in his speech that “A house divided against itself cannot stand”, meaning that a country divided against itself had the risk to disintegrate.
In 1858, Lincoln and Douglas accepted to participate in seven debates in different counties of Illinois during the senatorial campaign.