Once a boy went to a palace to ask a wise man what the secret of happiness is. After talking with the boy, the wise man asked the boy to look around the palace and return in two hours. "And , I want to ask you to do something,"said the wise man ."As you look around, carry this spoon with you without making the oil spill  ." The boy began walking up and down the stairs of the palace, and he kept his eyes on the spoon all the time. After two hours, he returned. "Well," asked the wise man, "what did you see in my palace?" The boy said that he had seen nothing. "Then go back and enjoy my wonderful world," said the wise man. The boy picked up the spoon and began to look around the palace again. This time, he saw many beautiful things in the palace. When he returned, the wise man asked, "but where are the drops of oil I give you?" The boy saw that the oil was gone. "There is only one piece of advice I can give you," said the wise man. "The secret of happiness is to see all wonders of the world and never to forget the drops of oil on the spoon." ,A, B, C, D,, . According to the passage, we can know   _   .
the boy didn't get the secret of the happiness at all the wise man told the boy what was the happiness, but not directly the secret of happiness is to see all wonders of the world the wise man said nothing