Such creatures have rarely been seen alive by man 这句话的结构是什么

Such creatures have rarely been seen alive by man .请问alive是什 Such creatures have rarely been seen alive by man as they li 新概念二82课中：Such creatures have rarely been seen alive by man. I have rarely seen such a beautiful sunset The machine is such as l have never seen before .这句话的意思是? have been seeing /have been seen/ have seen的用法. 在语法中见到这句话、、感觉很别扭、.I have never seen such an animal. 这房子少有这么多人.Rarely has there been such a crawd in this house很难 英语 Never in my life have I seen such a thing.的主谓宾是什么? I have seen this film twice with my friends.这句话的副词是什么? I have seen this film twice with my friends. 这句话的副词是什么?为什么呢? l am the fastest man alive这句话中alive 做什么成分,