动词原型一般用在祈使句;一般现在时的复数人称或第一人称;或情态动词can,could,may,need,must等的后面. 如 don't touch me, let's go I want to come back home. they need some book. I like it. I can complete it. 过去式用在刚刚发生或过去某个时间点发生的动作 I comleted my homework this afternoon. 过去分词用在现在完成时,过去完成时,以及被动语态,定语修饰中的被动语态等情况下,如: I have completed my homework. I had completed my homework before I had dinner. the baby was taken to my home(by...). I like this book signed by the autho