问题描述：
the building is said()last month
to be pulled down;to have been pulled down;being pulled down;having been pulled down应该选哪个?我觉得应该选完成时的被动语态,可这里有两个完成时的被动语态,应该选那个?求讲解,这两个完成时的被动语态有什么用法区别?求讲解
问题解答：
我来补答
the building is said(to have been pulled down)last month.
be said to do,据说.
be said that.据说.吗,根据以上两点,只能选择带有不定式的答案,只有前两项.
last month,说明事情发生在过去.而to be pulled down表示将来要发生.to have been pulled down表示发生在谓语动词is 前,发生在过去.所以答案应该是to have been pulled down
再问： 不是it is said to吗？be said to 怎么也可以呢？having been pulled down呢？只是因为他没有to所以不能选啊，他的用法是什么？
再答： 不是it is said to吗？be said to 怎么也可以呢？ 学语法不能太死，这个题目中不就是把 it 换成了 the building 吗，其他不都一样吗。就是因为这个用法，所以必须选择 带 to的选项 having been pulled down是动名词的完成被动式，表示动作发生在谓语动词之前且表被动。 举个例子： He forgot having been taken to Guangzhou when he was five years old. 他忘记五岁时曾被带到广州去过。
再问： 其实to have been done和having been done用法一样的吧，只是个别要加to和不加to的区别而已？除了said还有什么这么用啊？
再答： to have been done和having been done用法一样的吧，只是个别要加to和不加to的区别而已？ 嗯，主要区别在不定式和ing 上。 比如一些后面经常加to的单词，remember，forget，regret 等
