Professor：He'll be researching how bridges and culverts that have been installed to allow tidal waters to move underneath roads between the sea and the salt marshes. Well, they are often too small.

Student：I guess that would result in not enough tidel water flowing into the marshes to maintain the natural vegetation, right?

问题一：how bridges and culverts that have been installed to allow...这部分是how加名词加to do结构吗？我只知道how to do，这个结构。

【答】教授说的这个句子，至少有两个语法错误：

He'll be researching how bridges and culverts that have been installed to allow tidal waters to move underneath roads between the sea and the salt marshes.

1. 作为动词，research 后面可以跟名词、代词，但不能跟how 从句或how to do，这是中国人自己造的句子。

2. how bridges and culverts that have been installed to allow tidal waters：多了一个that，有了that 就成了定语从句，那么how bridges and culverts 就缺少谓语。此外，installed （安装）跟“大桥、涵洞”搭配，属于用词不当，应改为“built”。

问题二：请问not enough这里的not为什么没有提前到would后或者guess前，而且not enough与后面的to搭配，我感觉看上去，意思很奇怪。

【答】not 是否定enough的，enough 是修饰tidel water 的，所以not 跟前文的动词无关。

问题三：not enough tidel water flowing into the marshes to maintain the natural vegetation这一部分是一个flowing的动名词复合结构还是flowing...是后置定语，to...是目的状语还是不定式作定语，如果to是目的状语，那么他的逻辑主语难道是代词that吗？

【答】是动名词的复合结构，not enough tidel water 是其逻辑主语。整个动名词复合结构作result in 的宾语。 to maintain the natural vegetation 是目的状语，逻辑主语是句子的主语that。