Which of the following stirred discord between the north and the south?

Assuming you mean the US before the Civil War, slavery was a big issue. The North were all non-slave states, and the South were all slave states, but for a while there were equal numbers of slave and non-slave states. But then Texas, a slave state, was annexed in 1845, throwing off the balance of power.

Ithink it's b . narratives cannot be changed by other historians later