问一道 PREP 的题目

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

选什么?

我选D

E

ＤＩＮＧ

求解

the moderately sharp and jagged edges of the jaws function as teeth

红色部分是主语, function as 固定搭配,意思是:起到牙的作用