prep-4 请教

edwen

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

破解里似乎漏了这题得解释，哪位高人能谈一下吗

Gudjohnson

A: function as n. 固定用法
B: its 指代错
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

SC语法笔记是这么讲的

edwen

谢谢LS，不过问一下

您说的语法笔记是XDF的马