Option a is the correct answer. Devadatta was the Buddha's cousin and a close disciple in the early days of the Buddha's teaching. However, he later became jealous of the Buddha and wanted to become the leader of the Sangha. He tried to split the Sangha by forming his own group of followers. He also tried to harm Buddha on several occasions. After the Buddha's death, Devadatta continued to try to become the leader of the Sangha. However, he was unsuccessful and eventually died.