Quasars, at billions of light-years from Earth the most distant observable objects in the universe,(believed to be) the cores of galaxies in an early stage of development.
A) believed to be
B) are believed to be
PS:这里括号代替划线
答案说选B,因为A选项的句子结构是名词,插入语,-ed分词短语。因为A选项缺了谓语,所以错
我比较迷糊的是什么是-ed短语? 这题翻成中文我也会选B,因为是被动,不觉得是-ed分词短语
举个例子:Bush, the American president, selected this plan. 这句话中selected this plan算是-ed分词短语么?