hear, tell, learn, write , understand, forget, know, find , say, remember. I hear (= have heard) he
1)有些动词用一般现在时代替完成时：
hear,tell,learn,write,understand,forget,know,find,say, remember.
Ihear(=haveheard)hewillgotoLondon.
Iforget(=haveforgotten)howoldheis.
2)句型"Itis…since…"代替"Ithasbeen…since…"
3)Itis(=hasbeen)fiveyearssincewelastmet.
