动词过去式不规则变化：有那些单词是除双写改为单写加t的?“双写改为单写加t”这句话成立吗?

动词过去式不规则变化：有那些单词是除双写改为单写加t的?“双写改为单写加t”这句话成立吗?
“动词原形中的ell改为old,变成过去式.如：sell—sold,tell—told ”那么这句话成立吗?
动词过去式不规则变化的理论是什么?规律是什么?

动词变为过去式依旧是动词,当然还会有动词的特性.（1）一般情况下,动词词尾加 ed ,如： 　　work—worked； play—played；want— wanted； act—acted 　　
（2）以不发音的 e 结尾动词,动词词尾加 d,如： 　　live—lived； move—moved； decide—decided； decline—declined； hope—hoped； 　　
（3）以
+ y结尾的动词,把y变为i 再加ed,如： 　　studied tried copied justified cried carried embodied emptied 　　
（4）以一个
结尾的
动词,双写词尾
,再加 ed,如： 　　stopped begged fretted dragged dropped planned dotted dripped 　　
（5）注：
的过去式变化规律性不强,须多加记忆. 　　go - went,make - made,get - got ,buy - bought ,come - came ,fly-flew ,is/am-was,are-were ,
,bring-brought,do-did,teach-taught, think-thought, say-said,sit-sat. read-read, spend-spent, eat-ate,give-gave,tell-told,write-wrote,feel-felt,find-found,hear-heard,know-knew, 　　put-put,grow-grew,take-took,catch-caught,come-came,become-became,swim-swam,sweep—swept,sing—sang,draw—drew, 　　
以上的（1）至（4）条中的发音均有改变,具体分别有/d/ /t/ /id/. 　　而
的过去式的发音则略有不同,但是有些还是按照一定规律变化的.如以上的：make - made,get - got ,buy - bought ,come - came ,fly-flew ,bring-brought,teach-taught, think-thought, say-said,sit-sat. read-read, spend-spent,give-gave,tell-told,write-wrote,feel-felt,find-found,hear-heard,know-knew,put-put,grow-grew,take-took,catch-caught,become-became,swim-swam,sweep—swept,sing—sang,draw—drew