阅读下面的故事，根据故事内容回答问题：

    Once there lived a lion in the big mountain. He was very big and strong. He often ate the other animals. Every day he went out to look for food. The small animals in the mountain were all afraid of him. Near the mountain there were four bulls(公牛). They are friends, and they often worked and played together. The lion tried many times to catch them, but he could not do so. Every time he came near, the four bulls stood together to fight(战斗力) him. So he could do nothing to them.

    One day, the four bulls had a quarrel(争吵). After that each of them went his own way. When the lion saw this, he was happy. He caught one bull and ate him up. Then he caught another. One by one he caught all the four bulls and them up.