C. The people rebelled against high taxes
the ten northern tribes split away from King David's line because of a prophecy that said that Jeroboam would get the ten Northern tribes (because GOD promised David he would always have a descendant on the throne)
So Rehoboam got Judah and Benjamin as his kingdom.
The people split away because they asked Rehoboam to lower the taxes that were imposed on them my Solomon his father. His reply was "my little finger was thicker than my fathers waist. My father whipped you with whips, i will scourge you with brambles."
hope this helps