是am is are

是am is are be 是 is am are am is are是be动词吗? is、am、are是助动词吗? am is are 过去式 am is are. 用am,is,are am、is、are、 用am,is,are is am are is、be.am.are,哪个是单数,哪个是复数. 解释英语专用词,如be是am,is,are 英语中is am are do does的用法是? be是am is are 的原型吗 英语改否定句是把“is are am”怎么样? am is are do哪个是不同类的词 this+is+am+are 那个是不同类的词 is am are do,哪些是不同类单词