---Don’t litter the ground, boy! Look at the sign: Rubbish ______ into the dustbin.

---Sorry.

1. A.
   has throw
2. B.
   was throw
3. C.
   must throw
4. D.
   must be thrown

?Don't litter the ground, boy! Look at the sign "Rubbish ________ into the dustbin. "

?Sorry.

A. has throw

B. was throw

C. must throw

D. must be thrown