英语中,插入语定语从句和双层定语从句区别的问题.希望有人能解答以下的疑问.

题目

英语中,插入语定语从句和双层定语从句区别的问题.希望有人能解答以下的疑问.
英语中定语从句插入语问题：如此句：they pointed out the damage which they supposed had been done by last night's storm
这里的插入语they supposed一插入,岂不是多了一个谓语动词?这句话可以怎么改写呢?
还有双层定语从句中：He is the only person that we know who speaks so many foreign languages.岂不是可以看做一个插入语定语从句把,如who去掉.那么第一句不是就可以改写成：they pointed out the damage which they supposed that had been done by last night's storm了吗?而这就是双层定语从句啊!可书上说这样是错的.

答案

插入语是不可以算进一个句子中的,它属于复合句的一种,例如
What do you think is good for health?
they supposed是一个插入语表示这是主语的个人想法,猜想的
that we know指的就是这个 the only person,who speaks so many foreign languages.也是这个the only person
但they supposed指的是整个句子也就是,这些灾难是昨晚的风暴造成的,而不是the damage,所以不可以认为是双重定语对the damage的修饰