过去式：be---was fly---flew sit---sat teach---taught read-read
understand---understood think---thought make---made get---got
speand（没有这个单词,我就当spend咯）spend---spent write---wrote
come---came have---had pay---paid sell---sold bring---brought
leave---left sweep---swept see---saw take---took ring---rang
过去分词：be---been fly---flown sit---sat teach---taught read-read
understand---understood think---thought make---made get---got
speand（没有这个单词,我就当spend咯）spend---spent write---wrote
come---come have---had pay---paid sell---sold bring---brought
leave---left sweep---swept see---saw take---taken ring---rung