现在进行时,is,am,are + doing一般将来时,will,shall,be going to, be about to + do(动词原形)过去进行时,was,were + doing过去完成时,had + done(过去分词)一般过去时, did(过去式)
be +v.ing be going to +v.was/were +v.inghas/have +v.ppv.p