Don’t climb too high! You ________ yourself.

[　　]

They must ________ sitting in the room having a meeting all day long.

[　　]

The teacher thinks ________ a pity for him not to recite the poem.

[　　]

　　－What has happened?

　　－The window ________ but I haven’t found out who ________ it.

[　　]

We hadn’t been out long ________ she felt sick in the stomach.

[　　]

Tom was walking around with his letter ________ in his bag.

[　　]

Whom do these books ________?

[　　]

Some poems are difficult ________, but very interesting to read.

[　　]

The mother told her little son not to ________ fire.

[　　]

I’ve heard a warning over the radio ________ a hurricane may be ________ its way.

[　　]