UT4 被動式+who when which whom

John eats banana.

--> Banana is (a)   (eat) by John.

Marco does homework.

--> Homework is (a)   (do) by Marco.

The children played games.

--> Games were (a)   (play) by the children

The British speak English.

--> English is (a)   (speak) by the British.

Sally drew a picture.

A picture was (a)   (draw) by Sally.

I saw the monster.

--> The monster was seen by (a)  

We kicked the ball.

--> The ball was kicked by (a)   .

He bought a pen.

--> A pen was bought by (a)   .

The little girl asked a question.

--> A question was (a)   by the little girl.

Can you call Mr. Chan, ____ is the principal of our school?