问题补充:
Our teacher insisted that the key words worth paying attention before class.
A. be underlined
B. being underlined
C. to be underlined
D. to being underlined
答案:
A. be underlined
B. being underlined
(答案→)C. to be underlined
D. to being underlined
解析:考查虚拟语气。to是与pay attention连在一块的;(should)be underlined是insist的虚拟语气,故选C。