--Which of the following sentence is right?--I wonder _________.
---Who’s that at the door, Tony? ---________ is the postman, I think.
The plan they are talking about _________ improving greatly.
—I’m sorry, sir. I’ve made lots of mistakes in the monthly exam. — Never mind. ___________, the exam is a bit difficult.
—What can you see _________ the bridge, Millie? —Oh, an elephant is standing over there. Let’s go and see it.
— Must I turn off the gas after cooking? — Of course. You can never be________ careful with that.