A. 一般动词在词尾加-ed
cook -- cooked
play -- played
B. 以e结尾的动词在词尾加-d
live -- lived
C. 以辅音字母加y结尾的动词，先y变为i，再加-ed
fly -- flied
study -- studied
D. 末尾只有一个辅音字母的重读闭音节词，双写该辅音字母加-ed
stop -- stopped
plan -- planned
E. 不规则变化
swim -- swam
have -- had
F. be 动词变化
am -- was
is -- was
are -- were