National Public Radio asked exactly this question in a survey a year or so ago and they got the following principal responses back.

国家公共广播电台问过,完全相同的问题,在一次一年前的民意调查中,他们得到了如下的回复

耶鲁公开课 - 聆听音乐课程节选

I actually published a poem in the magazine two years ago.

两年前，我还在杂志中发表了一篇诗歌。

耶鲁文艺刊主编 - SpeakingMax英语口语达人

In fact, there's evidence that even thousands of years ago, Indian and Chinese healers were using a form of something that we would recognize as vaccination.

事实上,有证据表明在几千年前,印度和中国的医生就在使用一种,类似于疫苗的东西

耶鲁公开课 - 生物医学工程探索课程节选

The government has liberized the economy and that has of course been playing a role but the growth acceleration started almost a decade before that, so the factors are a little more complex.

印度政府让经济自由发展,这一决策显然是起了作用的,但在这一决策出现约10年前,印度经济的加速发展便开始了,所以经济腾飞的原因还比较复杂。

普林斯顿公开课 - 国际座谈会课程节选

And that's why I would've voted against the Constitution, I encouraged people to vote against the Constitution, and I know almost nobody, except professors in Paris and Lyon, who are for that Constitution that was defeated a year ago May twenty-ninth-- so,there.

这就是我为什么投票反对欧盟宪法条约,我鼓励人们投反对票,我知道除了那些巴黎和里昂的学究们,几乎没人支持,欧盟宪法条约,而他们在一年前的五月二十九日落败,就是这样

耶鲁公开课 - 1871年后的法国课程节选