The river smells terrible. People must_____ dirty things into it.

A. be prevented to throw         B. prevent from throwing      

C. prevent to throw             D. be prevented from throwing

The river smells terrible. People must ________ dirty things into it.

1. A.
   be stopped to throw
2. B.
   be stopped from throwing
3. C.
   stop to throw
4. D.
   stop from throwing

The river smells terrible．People must ________ dirty things in it．

1. A.
   be stopped from throwing
2. B.
   be stopped to throw
3. C.
   stop to throw
4. D.
   stop from throwing