know

　　I’ve known David for 20 years.

　　I hope we have taught our children to know right from wrong.

　　The old man has known both poverty and wealth.

　　know在教材中的意思为“知道,了解”,作动词用。在上面的三个句子中, know都作动词用,第一个know的意思为“认识”;第二个know的意思为“区分”;第三个know的意思为“亲身经历”。