A、The psychological immune system. B、Some man-made conditions. C、The optimistic view of the world. D、The human nature. A

From field studies to laboratory studies, we see that winning or losing an election, gaining or losing a romantic partner, getting or not getting a promotion, passing or not passing a college test, on and on, have far less impact, less intensity and much less duration than people expect them to have. Why? Because happiness can be synthesized, in other words, happiness can be made. Sir Thomas Brown wrote in 1642, "I am the happiest man alive. " What kind of remarkable machinery does this guy have in his head?      
    Well, it turns out it’s precisely the same remarkable machinery that all of us have. Human beings have something that we might think of as a " psychological immune system," a system of cognitive processes, largely non-conscious cognitive processes that help them change their views of the world, so that they can feel better about the worlds in which they find themselves. Like Sir Thomas, you have this machine. Unlike Sir Thomas, you seem not to know it. Natural happiness is what we get when we get what we wanted, and synthetic happiness is what we make when we don’t get what we wanted.
    I want to suggest to you that synthetic happiness is every bit as real and enduring as the kind of happiness you stumble upon when you get exactly what you were aiming for. We should have preferences that lead us into one future over another. But when those preferences drive us too hard and too fast because we have overrated the difference between these futures, we are at risk. When our ambition is bounded, it leads us to work joyfully. When our ambition is unbounded, it leads us to lie, to cheat, to steal, to hurt others, to sacrifice things of real value. When our fears are bounded, we’re cautious, and we’re thoughtful. When our fears are unbounded, we’re reckless, and we’re cowardly.
    The lesson I want to leave you with is that our longings and our worries are both to some degree overblown, because we have within us the capacity to manufacture the very commodity we are constantly chasing when we choose experience. Thank you.
    Questions 23 to 25 are based on the recording you have just heard.
    23.What phenomenon does the speaker introduce at the beginning of his talk?
    24.What makes people feel better about the world according to the speaker?
    25.When will our preferences make us at risk?