cost
cost-cost
run
ran / run
know
knew-known
do
did - done
cut
cut- cut
catch
caught - caught
have
had - had
swim
swam - swum
study
studied -studied
keep
kept - kept
spend
spent - spent
take
took - taken
leave
left - left
put
put-put
sleep
slept - slept
think
thought -thought
