这个句子里面有两个从句，have become是定语从句的动词，have been是宾语从句的动词。主句：主语conservation group, 谓语said，said后面到句子结尾是从句做宾语。宾语从句的主语是half the mammals，系动词have been，表语Australian species。其主语half the mammals 由that引导的定语从句 that have become extinct globally in the last 200 year修饰。...
定从中的谓语动词是 have become.而 have been是宾从中的谓语动词
主句的谓语动词是 said 这句话提主干就是： The group said half the mammals have been Australian species.定从： that have become extinct globally inthe...
