----How long are you staying? ----I don't know.___________.
I would rather buy a house in the beautiful and quiet suburb than _______ in the crowded city.
Of the two, I would prefer ____________ car, which is very easy for me to afford.
--- Jack, did you happen to see ____ black and ____ white cat?--- Is she missing? I told you to take care of her.
--- Who__________ it be that is knocking at the door? --- It ____________ be Father, but I’m not sure.
It is the test system, _________ the teachers, that is to blame for the heavy burden of middle school students nowadays in China.