Thetrapezeartistwhoranawaywiththeclownbrokeuptheliontamer'sheart.

动词搭配。break up打碎，终止，驱散；break away突然离开，放弃(习惯等)；break down毁掉，制服，中止；而本句要表达的意思是：……令训狮员非常伤心；所以应用break one's heart，选项C正确。