PREP 4

4. Although the turtle has been toothless for more than 150 million years, in some contemporary turtle species the moderately sharp and jagged edges of their horny jaws function for teeth.

A. their horny jaws function for teeth

B. its horny jaws function for teeth

C. its horny jaws function as do teeth

D the horny jaws function as teeth do

E the horny jaws function as teeth

正确答案是那个呢, 在PREP语法笔记里没有

I choose D

In some....species, ---> B and C: out

function for in A: strange

open to discuss

我选E，PREP里有答案的，如下：

A: function as n. 固定用法

B: its 指代错, 应该是species

C: 同上

D: function as n. 固定用法，这里不是as引导句子做比较

E: correct

注意：function as … 和 A do as B do 的逻辑意思区别

区分A do as B do和一些有as的固定搭配的区别