—Look! The telephone is broken. Someone damaged it       purpose.
—That may be right. But perhaps it was broken       accident

1. A.
   on; by
2. B.
   by; by
3. C.
   on; on
4. D.
   by; on

--Look! The telephone is broken. Someone damaged it ________ purpose.
--That may be right. But perhaps it was broken _________ accident.

---Look! The telephone is broken. Someone damaged it ________ purpose.

   ---That may be right. But perhaps it was broken _________ accident.

A. on; by                    B. by; by                     C. on; on                    D. by; on

--Look! The telephone is broken. Someone damaged it ________ purpose.

--That may be right. But perhaps it was broken _________ accident.

—Look! The telephone is broken. Someone damaged it       purpose.

—That may be right. But perhaps it was broken       accident.