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