You didn’t show the passage but I’m just gonna assume what the passage talked about.
Bleeding Kansas- Led by John Brown in which he revolted against slavery. This resulted in more tensions between abolitionists and pro-slavery ppl. Kansas was supposed to be deciding if it was a slave state or not based on popular sovereignty, but John Brown stepped in with others to revolt.
Uncle Tom’s Cabin- Exposed slavery through writing. Showed how slavery was harmful and inhumane.
Annexation of Texas- After the Mexican American War, tensions were rising because manifest destiny was a big thing. It was the concept that America should move west and imperialize other nations. This made pro slavery ppl believe they should annex Texas to spread slavery. This created more tensions between the north and south.