一般现在时,It smells good
一般过去时,it smelled (smelt)bad yestersay
现在进行时.Are you smelling sth
过去进行时,You were smelling sth last night
现在完成时i have smelled the delicious cake
过去完成时 i had semlled the delicious cake
一般将来 i am going to smell the delicious cake
过去将来i promised that i would smell the delicious cake in the near future