Question

(   ) 7. We must do something to stop people from      

A. to throw litter about    B. to throw litter into

C. throwing litter about    D. throwing litter into

Answer 1

7. C stop sb. from doing sth.和throw sth. about都为固定结构，分别表示"阻止某人做某事"和"乱扔东西"。