Mr. Green made a robot. He could say only one sentence—“There is no doubt (疑问) about it.” The robot always repeated the same words when you spoke to him.

    One day, Mr. Green needed lots of money and he took the robot to the market to sell him. “Who will buy my robot? He is very smart,” he shouted, “Twenty thousand dollars for my robot!”

    A man was surprised that he was asking for so much money. Instead of asking Mr. Green why he wanted so much money, he decided to speak to the robot. “Are you worth (值) twenty thousand dollars?” he asked the robot. “There is no double about it,” answered the robot.

    The man liked the robot's answer so much that he bought him and carried him home. But very soon he found that the robot could say nothing else. He was sorry he bought the robot. He stood in front of the robot and said, “How foolish I was to throw so much money away！”

    “There is no doubt about it,” said the robot.