大学英语：难句：Many of things that animals know how to

　　6. 难句：Many of things that animals know how to do they seem to know either without learning， or in some way which we cannot understand. 词句话为倒装语序，顺装应为：They seem to know many of things that animals know how to do， either without learning， or in some way which we cannot understand. 其中：either…or…表示“要么…要么…” 把此句可以翻译成：它们似乎知道很多动物做事的方法，这些方法要么不是靠学到的，要么就是以我们所不理解的方式知道的。

　　7. 重要句型：We never see frogs engaged in sport.

　　The owl always looks as if he were considering some important question.（as if的句型里出现了虚拟语气，由于是对现在的虚拟，所以采用了系动词were的形式）

　　Now，if he had had his wits about him， he would have known that there was no use in building a dam where there was no water.（此句为对过去虚拟的句型，原则为if条件句型用助动词had加上动词的过去分词形式，主句用情态动词would等加上have done 的形式；本句第二个had是have one‘s wits 这个词组的动词过去分词形式；另外，此处的there was no use in 后面只能接动词的ing 形式）

　　Animals think much while building their houses.（此句话为省略句型之所以用building，一方面是因为在时间状语从句里省略了语主句相同的主语animals和系动词are，另一方面是因为animals 可以发出build的动作，所以用主动的doing形式）