用could+inf,was/were+v.ing,had+p.p.,had been+v.ing ,would+inf
4个回答

yesterday I was watching TV while the doorbell was ringing.I walked to the door but suddenly I found someone had came into my house.i was scared and i could have gone to call the police on phone but unluckily my phone had been repairing outside these days.i do not know whether he would do something to hurt me.如果没理解错,这样应该可以了