I don’t remember _______ the book yesterday.
John, you play with the knife, or you hurt yourself.
---What ________ he say to you just now? ---He told me that he ________ his key in the room.
---Did you return Helen’s call? ---I didn’t need to _________I’ll see her tomorrow.
Now the air in our city is _______ than it used to be. Something must be done to stop it.
Most of the choices appear to be ones that you are familier with, but after taking second look, you will find that they are different.