附：过去分词的变化规则
　1. 规则动词：规则动词的过去分词与规则动词的过去式的构成规则相同。
  (1) 一般动词，在词尾直接加“ed”
study的过去分词    work---worked---worked  visit---visited---visited
  (2) 以“e”结尾的动词，只在词尾加“d”
    live---lived---lived 
  (3) 以“辅音字母 + y ”结尾的动词，将 “y” 变为 “i” ，再加“ed”
    study---studied---studied  cry---cried---cried
  (4) 重读闭音节结尾，末尾只有一个辅音字母，双写该辅音字母，再加“ed”
    stop---stopped---stopped  drop---dropped--dropped
　2. 不规则动词
  AAA型

burst burst burst       
hurt hurt hurt       
let let let
cut cut cut         
cost cost cost       
hit hit hit             
put put put         
set set set
shut shut shut         
spread spread spread

read read read(read原形和过去分词发音为/ri:d/,过去式发音为/red/)
　　AAB型
beat beat beaten
ABA型
become became become     
run ran run       
come came come
  ABB型

bring brought brought     
buy bought bought       
build built built
burn burnt burnt         
catch caught caught     
dig dug dug
feel felt felt             
fight fought fought       
find found found
hear heard heard         
hold held held         
keep kept kept
lay laid laid           
lead led led           
lose lost lost
　make made made       
  meet met met         
  sell sold sold
shoot shot shot           
sit sat sat           
stand stood stood
sweep swept swept         
teach taught taught     
tell told told
think thought thought         
win won won

  ABC型