不规则动词
can could
do did
think thought
know knew
go went
eat ate
sit sat
am/is was
are were
find found
see saw
tell told
sell sold
take took
hear heard
leave left
give gave
feel felt
come came
sing sang
drink drank
bring brought
have had
catch caught
swim swam
fly flew
sweep swept
smell swept
understand understund
规则（加ed)
例：play played
特殊
read read
hurt hurt
cut cut
put put
