1¡¢A snake is swallowing a frog over there.

A frog _____________ by a snake over there.

2¡¢Many chemical factories are polluting the drinking water.

The drinking water __________ by many chemical factories.

3¡¢The researchers are studying the life of the panda at present.

The life of the panda ___________ by researchers at present.

4¡¢The teacher is always praising Tom in public.

Tom _____________ in public by the teacher.

5¡¢The police are questioning the criminal now.

The criminal ___________ by the police now.