阅读下列材料，从A、B、C、D四个选项中选出最佳答案。
One day, a boy had a fight with one of hisclassmates. He went to his grandfather's home before school was over. He toldhim his story angrily. "He is really bad," the boy said, "and Ihate him."
The grandfather said slowly, "Let metell you a story. When I was a boy, I also sometimes hated others for what theydid…"
As the boy listened carefully, thegrandfather went on, "There are always two tigers inside my heart. One isgood and kind. He gets on well with everything around him. But the other is badand unfriendly. Even the smallest thing will make him angry. He fights witheveryone all the time, and for no reason. He can't think carefully because healways hates others. It is difficult to live with these two tigers inside myheart. They both try to control me."
The boy looked into his grandfather's eyesand asked, "Which tiger always controls you, grandfather?"
The old man said slowly and seriously, "Theone that I feed. I always feed the good and kind tiger, so I never hate othersand seldom get angry now. "