原型--过去式--过去分词--现在分词
fly-flew-flown-flying
return-returned-returned-returning
move-moved-moved-moving
miss-missed-missed-missing
sell-sold-sold-selling
原型--过去式--过去分词--现在分词
fly-flew-flown-flying
return-returned-returned-returning
move-moved-moved-moving
miss-missed-missed-missing
sell-sold-sold-selling