现在完成时,The Present Perfect Tense,现在完成时的基本结构,have/has+动词过去分词 （has用于第三人称单数,过去分词的变化： (1)规则变化,不规则动词的过去式以及过去分词巧记规律,AAA: put put put letlet let ABA: becomebecamebecome ABB: standstoodstood ABC: eat ateeaten,AAA,cost-cost-cost read-read-read put-put-put cut-cut-cut let-let-let set-set-set hit-hit-hit hurt-hurt-hurt 原形、过去式和过去分词的词形和读音都相同的单词，结尾字母一般是t或d。 特殊：动词read的过去式和过去分词虽然词形与原形一致，read-read-read，但发音分别是ri:d-red-red,有些动词的过去分词与原形是一样的: run-ran-run come-came-come become-became-become overcome-overcame-overcome,
