a/an all am/is/are and any as ask at back be been being but by can come could did do/does for get give go going good got had have/has how if in it just keep know let like little long look make may mean more most much my need never no not now of on one or other own place put say see seem should so some sort start still stop take tell than that the then there thing think this time to to too up used very want was/were way well what when who why will with work would you 练习答案