A、Family background. B、Chemistry. C、Age difference. D、A wise choice. D事实细节的找寻和判断。根据原文The key，he says…It is…are you ready? That i

Clark Warren has been a marriage counselor for 35 years -- long enough to help couples confront just about every domestic difficulty imaginable. On the personal side, he’s helped six close friends as they went through three divorces each. His own marriage, happily, has lasted 43 years -- and he and his wife, Marylyn, have raised three daughters who also enjoy happiness of marriage.
    So this is enough to say that Dr. Warren knows a fair bit about marriage -- from his practice, his friends, his own experience, and from his parents, who still liked to hold hands after 70 years together. And he thinks he knows what it is that makes or breaks a marriage.
    The key, he says, is not necessarily family background, or chemistry, or even how old people are when they marry. It is... are you ready? That is choosing wisely in the first place. "This choice has more to do with the eventual success of your marriage than everything else combined that you do after you get married," says this voice of experience. "If you choose someone who is highly compatible, it feels almost effortless; if you are mismatched, it’s all hard work and good intentions."