'That fellow of a Râganya asked me five questions, and I could not answer one of them.' The father said: 'As you have told me these questions of his, I do not know any one of them. If I knew these questions, how should I not have told you?

In plain words: Svetaketu says the king, a man of the warrior class, asked him five questions and he could not answer one. His father, Gautama, honestly admits that he does not know the answers either. If he had known them, he would have taught his son.