1.翻译句子，可以如何翻？
2.句子中出现三个动词，为何即有系动词，又有第三人称单数形式的动词？
你是否漏了个n。原句应该是：There are known knowns。详见维基百科https://en.wikipedia.org/wiki/There_are_known_knowns。
原文摘要：“Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones.”
即there are known knowns = there are things we know we know
are 动词
known 形容词
knowns 名词复数
